Is Synthetic Engine Oil Worth The Buck$?

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October 26, 2008

The need or value of using synthetic engine oils has been a controversy for nearly as long as they have been available. Originally they were wanted solely for their duration and ability to extend the need for an oil change by double or more.  Rumor has it, that when Mobile 1 came on the market, General Motors was approached and pitched on offering their customers’ vehicles that would only need an oil change once every year.  It was supposedly shot down by their dealers’ need to get the customers back in for regular service, a needed steady money maker.

Well, it appears synthetic is no longer thought of as an extender of oil maintenance as nearly every engine manufacturer warns against extending the duration of oil changes regardless.  Still there are people that believe it is possible and will work well.  I’m not one of those as I prefer to follow the manufacturer’s recommendations.  It may also be questionable as to the quality and type of filtering that we use today equaling the performance that these oils can apparently deliver.

So let’s see the balance, what other benefits can be found in using the higher priced oil? One of the prime benefits is the ability to operate more efficiently than regular oil brands in extreme temperatures, both high and low.  Generally this would be needed more in high performance gasoline engines or in engines exposed to extreme winter temperatures.  So are there any real gains to using synthetic or even partial synthetic in a motor home or RV towing vechicle application?  For heavy gas powered coaches or heavy pick-up trucks, probably.  While the engines are not what one might think of as high performance engines, they are subjected to extreme heat when accelerating the heavy vehicle and while climbing steep grades.  Diesel engines however, are a different story.  It is probably not as beneficial when used in the slower rotating engine that generally runs cooler.

So, is it of any benefit to using synthetic oils in modern diesel pushers? For the engine itself, perhaps little.  But, for the high RPM turbo chargers and for the built-in compressor units, it may be quite beneficial.  Turbo charger turbines turn at 90,000 to 220,000 RPM depending on the make, model and application.  The speeds and heat are so high that many bearings would not survive, thus the shafts are generally rotating in the bearing suspended on a thin film of oil.   Both cold starts and hot shutdowns can have their toll on the turbines and bearings.  Synthetic lube allows much colder starts and far hotter shutdowns, with no coking in the bearings that can happen when using conventional lube oil.  Likewise the superior lubrication qualities found in the synthetic at the extremes at either end of the thermometer protect the moving parts within the compressor and related components.

Let’s look at some of the good points and some of the bad.

Synthetic Oil Benefits

  • Runs cooler with reduced friction
  • Superior cold and hot engine performance
  • Resists the forming of sludge
  • May help to reduce fuel consumption

Synthetic Oil Drawbacks

  • High cost of purchasing
  • Not available at every service station
  • May not be advisable for use during break-in period

So, is it worth the extra money? In my opinion, probably not. That isn’t saying it is not a good or better lubrication, on the contrary it is a great product. No matter which brand it is. But, it is when the costs enter into the equation that it starts getting hazy. I mean, granted it will not coke in an overheated turbo charger, where it would with standard oil, but, if the engine and turbo were properly cooled down prior to shutdown, they would be virtually similar.

Having said this, I do use synthetic oil in my Cummins ISM and did in my previous ISC. I also use synthetic in my Escalade toad, our house stand-by generator, and previous personal vehicles. A motor home, in my opinion, whether gasoline or diesel, is subjected to infrequent use or long down periods and therefore may well support the added cost for synthetic oil use.

So, what’s your take? Do you use synthetic oil or conventional?

Looking At The Age Oil Question Lug_Nut Peter Mercer

Leave a Reply


  1. That’s really cool that synthetic oil will help you have hotter shutdowns and colder starts so that the bearings will last longer. My diesel truck needs to have some extra help because it’s old and getting worn down. I think that using some synthetic oil would help the bearings in my car last longer.

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  6. g2environmental

    YES, it’s worth the bucks because it’s eco-friendly and works efficiently. You can visit for the latest innovation about fuel. Check on the products and testimonials as well. Learn from the people who use synthetic oil.

    Hope it’ll help.

    Tags: Technology, Environment

  7. bpshand

    One must take anecdotal experience with a grain of salt. Particularly testimony about engine life experienced on vehicles owned using synthetic oil. Without equivalent experience with a vehicle using dino oil it’s fairly meaningless.

    My own experience with an ’85 Volvo with a 4 banger that went 340k miles, not smoking and passing CA smog before I gave it away in ’07 before a move would lead me to believe that regular oil and filter changes with a quality dino are overrated. Because, believe me, it often didn’t happen. The fact is that the running gear on these particular models have a rep for being fairly bullet-proof. Hell, it even had the original clutch and everything that made it go worked well. It wasn’t a pretty vehicle anymore though, inside or out.

    So make and model of equipment as well as plain luck can have as much influence on particular results as the type of oil used. That said, based on the performance specs and actual cost, I’m going to be switching to synthetics for all my motor driven equipment – RV, cars, yard tractor. If I get better mileage with any vehicles so much the better.

  8. carverant

    Lug-nut. I have a 1990 cummins 3 speed auto,We bought a 2500# truck camper 3 yrs ago and went to the west coast, milage was at best 12/13. Came home added AMSOIL heavy duty to transmission and rear end milage increased to 14/15 on trip to Wisconsin, next year added Amsoil to engine with over 300,000 miles and mpg went to 16/18, now the lesser milage was of course in our Va mountains and the greater on flatter land. I will also admit that we try to drive 5mph under posted speed. I had heard all sorts of bad things about adding syn oil to high milage engines, causing leaks etc but I have not had that experience. I do add about a quart every 7000 miles and change every 12/15 thousand milesand the filter alone at about 7000..My motorcycle and van and lawnmower also have Amsoil, so I’m hooked.

  9. Earl Hall, I agree with you entirely regarding the synthetic oil maintaining a film longer than that of regular oil. This helps make it a great choice for an RV application. With the long stand down times involved it help to provide better surface protection. Thanks for your insightful comment and your great input.

  10. Earl Hall

    With respect to Ron Caroll’s comments in Nov 08 on aircraft engines, my understanding is that synthetic oils leave a film of oil longer after they drain down than regular oils. That is why there is less wear on start-up. If that is the case, the advice about using regular oil to prevent internal rust from condensation over winter is in error and based on someone’s assumption that synthetics flow off cylinder walls faster than regular oils. I think that the person giving the ‘regular oil’ advice should be challenged to prove the point.

  11. Richard Kidder, There are a lot of Amsoil supporters it appears. Though I have not had experience with their product, I’m getting to think it might be worth the investigation. Thank you for sharing your experience with it and for your great input.

  12. Richard Kidder

    I have used Synthetic for the past 35 yrs. AMSOIL and now there great filters…My greatest succes was with our 89 Volvo turbo wagon which had 300k miles on it as well as the original turbo.. Volvo said ya the turbo would work but the blow would be very low at this age.. The tech test it on the road and the responce was very good , he was very impressed, as it had very good pressure…. I also have a 94 Mazda pickup(Ford Ranger) with the 4 ltr engine, it now has 310k miles, burns no oil , leaks a little.. Starts and Runs very well It still gets from 18-21 mpg.
    My 1999Seabreeze has 130k and runs great..All are on Amsoil in the crankcase,Rear end ,Transmission.. I change oil about 10k mi. and the filters aroumd 5k. I use the EA filters which are good for 12k thefilter is good to about 10-15 micron…

  13. Larry, The heat you mention experienced in turbines is somewhat similar to that of a fully spooled turbo charger. Though, perhaps cooler, most people don’t think of the high temeratures experienced in a turbo pulling a grade at 130,000 RPM. I agree, synthetic oil has advantages in this application. Thank you for you valued input on this topic.

  14. Larry

    Synthetic Oil is worth the money in any applications, as stated above by many. I worked for years on the LM2500 Gas Turbines in the navy (Jet engine) they could not keep them from melting down until Synthetic oil. We used to have them on a constant filtration system but the oil in some of these engines were not changed out in over 15,000 hours. Now you have to realize the hot section in these engines average 1500 degrees.
    After breaking on all vehicles 5K they get synthetic oil. I usually average an increase in gas milage of 1 – 3 MPG. and I change the filter every 3K but the full oil change only happens at 15k, unless there is some other reason to do in sooner.

  15. Mort, You bring up a great point. There seems to be many soft benefits supporting the use of syn oil. Thank you for your great comment and participation.

  16. Mort

    One HUGE factor everybody seems to take into consideration is that good synthetics burn very clean leaving almost 90% less carbon on your valves.
    How much is a valve job on my 32valve V-8 with aluminium heads? Thousands.
    Way to look at this for me is one less thing to worry about.
    If both syn and non syn cost the same price almost everyone would go syn. the more miles you drive the more synth. pays you back.
    Synth use since 1979. Mort

  17. Pat, Great and interesting input. This really shows that there are two or more camps on this issue. Thank you for sharing your ideas and input.

  18. Kevin Austin, Wow, impressive results. But how do you know it runs cooler withiout a reasonable benchmark? The milage claims are also big too. I don’t know that all the gain could necessarily be contributed to the syn oil. I agree with your shortening the oil change frequency from what your tech says. I, and the engine manufacturers too, question the extended milage issue. Thank you for your participation and your great input.

  19. Mike Austin, You raise a good point, however, Cummins actually has a branded Cummins named Valoline 100% synthetic oil, and has for years. The factory school tech teacher may have felt that way, however, it is a mixed bag as far as whether the extra costs are justified. Believe me, you can find Cummins tech’s that will swear by the syn oil. Who’s right, is anybodys guess, hence this blog. Thank you for your great input.

  20. Pat

    I ran Shell Rotella T 15w40 in my own Class 8 rig back in the early 1980s. Certainly do not consider it a high end petroleum product, considering what is available today. It is a good Dino motor oil, but no where as good as Mobil 1. The Shell Rotella T synthetic (hydrocracked – base stock 3) is a excellent oil but not a true synthetic.

  21. Kevin Austin

    I have used synthetic oil for two years in my 1999 Fleetwood Southwind / gas V-10 and found the engine to run much cooler. In addition we have seen a 1.5 to 2 mpg improvement since switching to synthetic oil. My service tech. recomends changing the synthetic oil every 15000 miles; however, I chickened out at 10K.

    Any thoughts?

  22. Mike Austin

    I would be interested in hearing from the Cummins and CAT folks who have Big Rig Diesel pushers. Our 2008 Allegro Bus came with a Cummins 425 horsepower engine and we went through the Cummins factory school when we bought the motor home. Cummins was emphatic about the use of a high end petroleum product such as Shell Rotella T 15W40 and made the statement that you will have minimal problems if you change your oil and filters as recommended and that synthetic oil was not required and was not worth the added expense. I have not heard anything on the CAT side and would be interested if anyone on the blog has any input into this interesting discussion.
    Thanks for listening to our input.

  23. Gerry, Thanks for sharing your experience with synthetic oil. It certainly supports its use and possibly justifies the cost. Great input, thanks again.

  24. gerry rogers

    while working at SFO for Pan Am we tested synthetic oil on 707’s for 1yr (FAA over seeing the testing) the engine overhauls went from 2500 hrs to 25,000 hrs. Hot Rod about 3yrs ago tested a used car, dyno tested it , changed oil to mobil 1 retested and gaind 10 hp. I have mb1 in my motor home, honda crv, corvette, ford f 250 . enough? thats all I have running at this time. Gerry

  25. JP, There are many benefits to synthetic oil other than just extending the service internval. Most, if not all, manufacturers do not support extended oil changes. If you are referring to a gas powered coach, it might well help the engine run better, longer and have less repairs in the long run. Thanks for your input.

  26. JP

    This is a very interesting discussion as my new class A will soon be due for it’s 3000 mile service. The dealer’s mechanic advised me to use synthetics, which seems logical except for a couple of items. The owners manual has a statement “Failure to perform scheduled maintenance on ….. will invalidate the …. warranty.” The maintenance schedule calls for oil and filter change at 3000 mile intervals. It seems to me that using a synthetic product is not cost effective while trying to keep the warranty in effect. If I had 200K miles on the class A, it would not make any difference.

  27. John Shelton, You make a valid point, however, a gas engine can run hard and hot pulling a large coach up a long grade. Likewise the turbo charger of a diesel engine can reach extreme heat also when climbing steep grades. Is it worth the buck? Perhaps yes, perhaps no. It may very well have saved or reduced repair costs within the ownership of a person, but there is no real way of telling. It’s up to each owner. After all, it only costs extra once a year, if you do low yearly milage. Thanks for your well thought out comment.

  28. John Shelton

    My comment here is not intended to support a theory that synthetic motor oil may – or may not – be more suitable in a motorhome or trailer power unit than petroleum based motor oil. My comment refers you to the title of the article, “Is Synthetic Engine Oil Worth The Buck$?” Everyone here answered a question as to whether synthetic oil is “better” than petroleum based oil, but failed to address whether it was actually economically cheaper. The answer to this question is probably, “no”. The original motorhome owner only drives their motorhome a limited number of miles and keeps it for a limited number of years such that there is considerably more money spent on the difference between the price of the two options without any measurable amount saved on repairs or fuel costs to offset the additional cost of synthetic oil. If the vehicles were subject to high mileage and/or severe operating conditions such that the use of synthetic oil extended the overhaul interval or resulted in a significant reduction in upkeep expenses in some other way then it may be “Worth the Buck$”, but there is probably no $ payback for the typical motorhome owner.

  29. Mike, Thanks for sharing that with us and for your input.

  30. I have used mobile 1 in my 2002 VW golf tdi sence new now it has 230,000. miles and still runs great.

  31. Judging by the comments, it seems that synthetic oil use may be very worth the buck$. Great input and information.

  32. Bob Davis, Great positive statement supporting synthetic oil use. I appreciate your interest and input.

  33. Bob Davis

    To All, Synthetic oil was developed originally(BEFORE NASA) for jet engines because of the high heat generated by rpm friction. In world war II Germany introduced the jet in a fighter plane, it carried almost as much petroleum based oil as it did fuel. It never caught on because it burned to much oil due to heat. If synthetic had not been invented we would not have a commercial airplane industry today. Synthetic oil can be(and should be) used in any engine i know of built by man.

    Good Luck

    Bob Davis

  34. Rick, Thanks for the link. Good supportive material for synthetic oil.

  35. Ron, You, as many, add to the information, which is appreciated. As a fellow pilot I understand your thoughts. I have not used synthetic oil in any reciprocating aircraft engine, therefore can not comment with any insight. I thank you for your great input.

  36. galaxiexl, Great input. It speaks for itself. Thank you.

  37. Ron Carroll

    Admittedly I am a rather inexperienced RV owner/driver, and extremely interested in the use of synthetic oil in my vehicles, for all of those good reasons stated by Bob Davis , on October 1st. – I’m sold on the idea.

    However, as a light plane pilot with 19 years flying my own planes, I have been warned by those in a position to know, that the use of synthetic oils are not recommended in aircraft engines, for very good reason. The last thing you want to happen is an in-flight problem with your airplane engine.

    Most of us involved in flying for personal use, as opposed to flying professionally, usually don’t fly the planes much, if any, during the winter. I’ll get feedback on this statement from other pilots, but ‘generally’ speaking, its mostly not good for flying when the weather could change and be threatening.

    Therefore, we store the planes for the winter, with no engine running for what could be several months. Atmospheric changes during this period will go from highs to lows to highs. These changes cause the ambient air to move into and out of the engine on a daily basis. The water vapors in that air tends to condense on the engine’s internal metals. Because synthetic oil does not provide a lasting ‘film’ of oil, it drains off the inner surfaces, leaving them unprotected, and at risk of oxidation (rust).

    What has this to do with the use of synthetic oil in our RV, you ask. The only thing that applies here is that some RVers. like private pilots, don’t use their vehicles much during the winter months. And the automotive type engines are subjected to the same threat as aircraft engines – oxidation.

    The bottom line here is that if you don’t use your RV much in the winter, you really shouldn’t leave it unprotected by having a non-petroleum based oil in the crankcase. On the otherhand, if you do use your RV throughout the winter months, then you will not have this problem because the temperatures reached during the use is enough to keep the water vaporized and disposed of through the crankcase breather by evaporation.

    Although I am totally in favor of the use of synthetic oil in my car that is driven year-round, I believe that for the reasons above, I cannot use it in my gas engined RV.

    I’m obviously not a technical writer, but you may or may not get the idea, right or wrong, but worth consideration.

    Never an aircraft engine failure or internal damage with the use of recommended petroleum based lubricants.


  38. galaxiexl

    Synthetic Oil was developed for NASA”s Shuttle and Hubble telescope programs.Lubricants cannot be changed in absolute zero conditions.
    Those of you with Martin Marietta and other contracters know the value of NASA’s product developement and research.
    Without NASA’s research we would not have cell phones,teflon,or even WD-40 which was developed to keep water off the external tanks (Water Displacement formula 40)How about cordless drills?developed again through Black and Decker for astronauts to assemble parts on EVA’s.
    Synthetic Oil is all it is cracked up to be and more.I agree a Diesel would not benefit as much as a Gas Burner.
    Synthetic will not freeze,it keeps it’s viscosity regardless.Changing from Crude stock to Synthetic buys about one additional horsepower.
    Yep,it’s out there and extended oil changes are real.ONCE A YEAR with a filter change 3 to 4 times a year.The only thing that can happen to Synthetic is it will eventually get fouled and contaminated with grit and dirt.
    I personally Run ROYAL PURPLE in my 96′ Accord 4 Cyl.Along with an AGM battery and K and N Filter.I know I can get in my car in 40 below conditions and it will fire right up without fail.
    Thats my story and I’m sticking to it………………..

  39. mr_whit, Thank you for sharing your experience with Amsoil with us. It has certainly been around for a long time. As I stated, there are other great synthetic oils on the market today, and Amsoil is one. Thanks for your input.

  40. Hi Bob, AMSOIL was the first (1972) to develop 100% synthetic oil. I changed all my oils (engine, trans, transfer, front & rear ends), been running the same oil for 22,700 miles (once a year engine oil change) and am getting 24 miles/gal pulling a 35′ 5th wheel. AMSOIL has identified many problems with petrolem oils and developed 100% synthetic oil to remove the problems. For more info, check out my web site

  41. Lug_Nut

    Bob Davis, I agree. There are other brands that are certainly equal to Mobil 1. I just had to use one and it is the product I happened to choose. Thanks for your input.

  42. Bob Davis

    Lug Nut, Other synthetic oils may have the same benefits. You should check the
    specification and compare to Mobil for gas engines 1 or Delvac 1 For diesel engines.


  43. Mike, That is a strange happening. Synthetic oil really can’t make that large a change to fuel mileage. I am happy for you that you do get these results. Thank you for sharing your story with us. All the best.

  44. Michael Turner

    I have a high regard for the fuel savings of synthetics. My ten year old Jeep shows no deterioration in performance or fuel economy after 230,000 miles. And I get about 2 to 3 mpg better than other similar cars I know of whose owners use regular oil.

    However, my 2007 Cummins is another story. They require an upgraded classification of oil. On the second change, my dealer’s service department was unable to get the oil in synthetic, so they used regular oil that did have the required classification. The service people would not show their faces, and the desk clerk said over and over: “It will not hurt your engine, it will not hurt your engine.”

    Yea. Instantly went from 19.5 to 20 miles per gallon, down to 13 to 16 mpg unloaded, and mostly 14 mpg down to 9 to 12 m[g pulling the fifth wheel. I was frantic. Changed back to synthetic myself, way before the change was due. Then sweated it out. After a couple thousand miles, I have my mileage back better than ever. We now get around 22 mpg at higher speeds than we used to drive. Don’t know about pulling the fiver yet, will have to wait till next trip.

    I have no explaination for why the difference is so great. Perhaps no one else in the world will see such a difference. But it happened to me. And this guy will never again let anyone else change his oil.


  45. Bob, Thanks for the great list of benefits found using Mobil 1. Do you feel that any of these benefits are not found in any other brand of synthetic oil? Just curious. Thank you for your input.

  46. Bob Davis

    Synthetic oil is well worth its cost !

    Mobil 1
    Advantages and Potential Benefits
    1. Meets or exceeds demanding specifications of major OEMs
    2. Outstanding thermal and oxidation stability
    3. Reduced low temperature sludge build-up and high temperature deposits
    4. Enhanced film strength at high temperatures
    5. Reduced engine scuffing and bore polishing
    6. Inherent stay-in-grade shear stability
    7. Wear protection and reduced oil consumption; maintains viscosity in severe, high temperature service
    8. Advanced formulation and viscometrics Improved fuel economy
    9. Low volatility Reduced oil consumption
    10.Exceptional low temperature pumpability
    11. Easier engine start-up and reduced wear
    12. Enhanced TBN quality reserve Deposit control and extended drain capability
    13. Outstanding resistance to corrosion
    14. Extended life of critical wear surfaces
    15. Long drain capability Increased operating efficiency and lower overall cost
    16. Component compatibility
    17. Longer gasket and seal life, extended service intervals

  47. Hi John, Always great to hear from you, and as usual you bring some great challenging information to the fore front. I’ve heard of some like affects experienced by some synthetic oil users. I do believe you have hit on a valid point. Thanks for bringing this up, and perhaps some other readers can offer additional insight into this issue. Again, thanks John.

  48. John

    Hi Lug_Nut,
    Regarding RW’s experience with oil on his car. When I was talking to my local Ford dealer about synthetic oil last week, he mentioned that synthetic has more of a tenedency to find a leak than mineral based oil. He have may a liner or rings that may need replacing or it could be a valve cover gasket. A Cummins dealer should be able to shed some light on it.
    Keep the great articles coming!


  49. Hi RW, I can not explain that. The Cummins branded Valvoline sythetic oil only comes in 5-40. What brand oil did you use? Thank you for sharing your experience with us.

  50. John, That’s interesting that moly is also in some other lube products. Actually that may be an interesting topic. A topic dealing with gear oils and greases. Thanks for the great input.

  51. R W Bennett

    Hi To All
    I used Mobil 1 turbo truck diesel 15-40 in my cummins 370 hp at about 24000 miles. All okay until about 2400 miles later and then oil came out all over my car not a whole lot but it did come out. I switch back to regular 15-40 and never got oil on my car again after about 4000 miles. I never got oil on my car before I used Mobil 1 either. The engine may have not been broken in, I don,t know!

    R W
    PS: First time on RV net.

  52. John

    One comment above mentioned moly as the key ingredient in synthetic oil.
    It also comes in chassis component lubricants (grease) that I’ve been using
    for over twenty five years. It seems to last longer than earlier lubes and also has excellent water repelling qualities. Used it on wheel bearings, U-joints steering/suspension components, fifth wheel plates, trailer hitches, great for extreme pressure use.


  53. Bill, I’m not surprised that some fleets are in fact running the extra miles on the synthetic. This would make sense especially if your fleet was off warranty. Thanks for the great information.

  54. Mac, You certainly are a synthetic oil supporter, and apparently for good reason. A 20 minute full load on the engine would really push the heat up. Thank you for sharing your synthetic oil uses with us.

  55. Sid B., Yes most manufacturers want oil changes as specified for any oil, whether you use synthetic or not. I agrre, I don’t mind changing as scheduled. That for my motor home is 15,000 miles. Thanks for the input.

  56. Dan, It seems farm tractors would not be an ideal application for synthetic oil, but, as you prove, it is. Thank you for your input.

  57. Bill Baxter

    Sorry LUGNUT but many of the trucking companies are on extended oil change intervals. The filter is changed at some interval usually 10K miles and oil sampled. Changes are based on sample results. One local company has DD S60 pushing 1.5 million miles with,at present, a 75K mile oil change interval.
    Our VW Jetta TDI came from the factory with synthetic oil. And it has always had synthetic oil at the factory recommended oil change interval of 10K miles.
    Ran an 1987 Aerostar, 3.0L V6, on synthetic oil after the first two oil changes. sold the vehicle after 195K miles and ten years. Engine was slowly dying. Mileage down from 26 MPG to 23 MPG. Oil usage was increasing at a quart every 2000-2500 miles with an oil change interval of 10K miles, filter every 5K miles.
    My observations are that synthetic oil seems to be beneficial to all engines.
    In the MCI conversion synthetic for wheel bearings and differential. Replacement engine, a 4 stroke, will get synthetic as will the transmission.
    All of that said, great discussion and great replies.
    Thanks for your efforts

  58. I have a 1996 Southwind on a 95 Chevy chassis with a 454. When we had the engine rebuilt a few years ago we didn’t go back “stock”. 🙂

    Any 20,000 pound gas engine motorhome is putting the engine to “Severe Service”. In my case it’s also a “high performance” engine. The same could be said for the transmission. On some mountain roads we find ourselves at wide-open-throttle for 20 minutes at 40 MPH in 2nd gear, and I imagine many others do likewise.

    I run Mobile 1 15-50 and have good results with it. I used Castrol 20-50 at first, and oil analysis revealed it was breaking down badly (viscosity) within 3000 miles. Since the switch to Mobile 1 no problems. We also run full synthetic in the transmission and rear end.

  59. Sid Burklund

    My wife and I own a 2006 – 6L Ford Turbo Diesel Super Duty and have been using Mobile 1 Turbo Diesel exclusively after bread in. We pull a 37 foot 15,000# fiver and live in the pacific northwest were high mountain passes are the norm.
    When I am on a long steep pull running 3800 RPM and 30# of boost on a hot day you can bet I want synthetic oil in our engine. I also change oil every 5000 miles per Ford recomendations.
    When you have as much money tied up in rolling stock as is customery in RV’s I think it only makes sence to use synthetics.

  60. Dan Steiert

    Great topic,synthetic oil,we farm here in Canada and use it in tractors,vehicles,motorhome(class A)etc.great stuff,saves money,and wear and tear all around.The additive in synthetic oil is Molybdinum Disulfide,this is what gives the improved engine etc.performance,have a great day,Dan.

  61. Hi John, Wow, you did record a fuel savings. That’s great. I can’t say I have yet, or perhaps unable to measure it. Your theory on savings over the long haul may well be true. As always thanks John, great input.

  62. Ham Radio, I use it in my standby home genset, but not my on board Onan, yet. Thanks for the comment.

  63. John

    Hi Lug_Nut,

    Great article and a popular one at that! I tried synthetic for the first time this past summer on a trip to Oregon from B.C. Did the service myself and noticed an immediate improvement from the first start up.
    Also noticed an improvement in fuel mileage of 1-2 miles more per gallon. Better lubricating properties means less friction which means longer engine life, cooler operation and less fuel consumption. I’ve been running synthetic in the transmission and diff. for a few years.
    Did the wife’s car too and increased fuel mileage by about 28-30 more miles per tank over the last six months.
    I think the cost of synthetic actually saves you money in the long run.

    I’m sold on synthetic.


  64. Ham Radio

    Great blog. Thanks to all.

    We use synthetic in personal power equipment such as generators. We do a lot of emergency communications and have never had a genny fail under high usage conditions, such as up to 48 hours straight running with desert daytime temperatures over 100 degrees.

  65. Richard H., Amsoil certainly is a well known product. My choice of featuring Mobile 1 was only to use a product that people may be able to identify. As I stated, any good quality synthetic would deliver the same performance. Thank you for your kind words and for your most valued input. Your comment is greatly appreciated.

  66. Richard H. Zentgraf

    I enjoy your daily blog and I find your daily blogs and suggestions timely and well researched. At age 75 I just have to add the following comment about sythhetic oil.

    All this talk about Mobil 1. They were a copycat. Amsoil was the pioneer 3 years earlier. From theit very first 10W/30 introduction their warrantee has been clearly posted on their containers. “One year of use or 25,000 mies”. The same warranty is still in use today.

    I have been using their product for 30 years or so wit the (once a year oil change) and have greatly benefitted from their superior product, have save significent $$$ in labor and gas milaege but have made a contributation toward toward energy independence.

    I have no financial benefit from suggesting this company or their product. They are simply the cutting edge on automotive lubricants and have been so for over 30 years. .Check them out at AMSOIL.COM or you may drop me a note at [email protected].

  67. Nevin, All I can say is, Wow! This is certainly against all warranty policies from all manufacturers, however, if you are passed the warranty period, I guess it’s up to you. Thanks for a very interesting comment and a whole new view of the hidden features of synthetic oil.

  68. Nevin Daniel

    I bought a 1999 Ford, F450, crew cab, dually, diesel, with roughly 56,000 miles from a gentlman who had installed Amsoil synthetic oil in the engine, transmission, rear end, air filter by Amsoill, and a by-pass filter system from Amsoil. I now have 155,000 miles on the vehicle with the same oil. Every 6 months a filter gets changed, another every year, and the oil get analysed every 20,000 mile. Every analysis for the last 6 years has had well below normal readings for every one of 20 tests. Of course, each filter change does requier topping off with new oil, but I add only about a gallon a year. Why would anyone not want to save petroleum oil for those who must use it and convert to synthetic if only to get away from petroleum oil.
    PS I have pulled a 37′ 18,000 lb 5th wheel RV for the last 7 yrs without problem.

  69. Thomas, Your comment is a good statement supporting the use of sythetic oil. Thanks for sharing your experience with us.t

  70. Walt, Good information and advice. Thank you for your valued input.

  71. Ernie, Good advice on break-in period. Thanks for the input.

  72. Walt Labree

    If you are considering synthetic motor oils or other syntheyic lubricants as I use, you need to consider:

    Oil sampling that is provided by the engine manufactures (at least by CAT). Truck fleet owners & others use oil sampling to determine the contaments in their oil at specific periods and this allows them to extend their oil change cycles. I would recomend that the oil filters be changed as required by the engine manufactures. Oil sampleling is not expensive, and allows the experts to evaluate your oil to detremine if any problems could be happening in the near future, allowing you to correct those problems before they mature with the least expense.

  73. Ernie Gavelin

    I have used synthetic oil in all my RV’s for the past 20 plus you state it gives better protection in high heat situations,no sludge or oxidation. But I caution using it during the engine break in period,it can take as much as 30,000 plus miles for the rings to seat properly (which means adding oil regularly) I did not heed my own advice,and changed to synthetic after 3,000 miles on a Ford 6.8 V10 in a Class a motorhome that we fultime in,it now has 45,000 miles on it and the oil consumpion is just now normal.I recommend 8 to 10,000 miles with regular oil then change to synthetic and only if there is very little oil consumption.

  74. Thomas Becher

    according to the duramax book. “when the change oil light comes on it means service is required with the next 600 miles. It is possible that driving in the best conditions it may indicate that service is necessary for over a year.However your engine oil and filter must be changed at least once a year” I use Mobil 1 turbo diesel and firmly believe in it. I had a 1985 Ford 460 in a C that used a quart in 500 miles. I switched to MB1 20/50 and never used oil between changes. My daughter now has it and it gets changed once a year 6 quarts x 6 bucks=36 bucks Big deal that engines got almost 200k on it. Don’t really know if it would have made it this far on regular motor oil

  75. Brooker Smith, Sounds like the oxidation issue may be a good reason to consider sythetic oil given the amount that the average RV sits idle. Thanks for your great input.

  76. Brooker Smith

    For the folks who do not know about oxidation it is real and an issue when you do not use the engine every day, as for the extra miles before an oil change it is also very true. As for sludge this is a main reason i use mobil 1 oil in all of my cars and trucks ( motor,trans.rear)

  77. LEH, Yes, the interm filter element is a great idea. The resistance of sludge built up is a top feature of sythetic oil. Thank you for the kind words and I’m glad you enkoyed the blog.

  78. Phil, You bring up an excellent point, there are many autos, mainly high performance, that come new with sythetic oil already in. Thanks for your input,

  79. LEH

    I, too, have seen reputable studies where synthetic was tested against conventional motor oils and had less breakdown after 10k than the conventional after 5k. I also have read it is a good idea to change the oil filter at 5k. I ran synthetic in my Saabs for over 20 years. Started doing it before intercoolers were used, and it did prevent coking. I also use it in my Honda Element, and change at 10k, which is the factory recommendation. I believe Honda uses semisynthetic for their private label.

    Re. the oxidation issue. I don’t know if this is the same, but on my Saabs there was never any sludge buildup on the filler cap when using synthetic, while other Saabs I checked did have it.

    Lug_Nut, thanks for a great blog! LEH

    ps: I am running Delo in my DP (300hp Cat). Cost/ perceived benefit ratio doesn’t pencil out for that quantity, imo.

  80. phil willen

    Many years ago I read an SAE bulletin that stated tests showed that Mobil1 after 20,000 miles had the same properties as standard oil at 7500. Porsche, Corvette, BMW, etc. come with M1 as factory fills. I use it in all my vehicles, even in the generator. Change once a year and change the filter at 6 months. Considering the investment in rolling stock, it’s cheap insurance.

  81. Tireman9, Great to hear of your experience over the years with sythetic oil. Your application seemed very demanding on any oil product. Great input, thank you.

  82. Bob, I’m not familiar with the oxidation issue as apposed to regular motor oil, but appreciate your valued input.

  83. Tireman9

    I ran a Camaro in endurance (3 to 24 hour) road course races for a number of years. Always ran synthetic in enginer, trans and rear-end, as insurance for high heat situation. Running non-synthetic cost me a race one time so never considered using standard lube again.
    For my new Class-C I will probably run name brand oil that meets API standards. HOWEVER for the Auto Trans and the rear-end I plan on changing to 100% Synthetic next spring (5,000 miles).
    My experience with synthetic is that it can handle the long term heat in the trans and rear end better than non-synthetic. Cost is less of an issue as I am not changing it every 3-5,000 mi.

  84. Bob Davis

    You forgot the most important benefit of Mobil 1. IT PREVENTS OXIDATION!
    Oxidation is our worst enemy: Engines and our BODY.
    It defiantly is worth the cost. If it would prevent oxidation in my body i would drink some.