beware of b20

beware of b20Beware of B20 fuel.

If you have a diesel-powered motorhome, or tow vehicle, you are probably used to seeing fuel pumps labeled with biodiesel content. Typically, they are marked with B-5 and up to B20.  This is the percentage of the oilseed produced biodiesel that is in the fuel.  Like the “E” (Ethanol) that many gasoline pumps dispense, we take little notice.  However, the biodiesel may not be that diesel-engine friendly, or in particular, to those diesel-powered RV’s.

First, if you have a Mercedes diesel engine, as many RV’s are now using, you had better read your manual. These engines will operate on up to B-5, but not above.  The use of B20 fuel may do serious damage to the motor and may not be covered by the factory warranty.

Newer Cummins engines, say models in the past 10 years, are capable of operating on any biodiesel up to B20. However, there are precautions to observe for the use of B20.  Minor issues with possible earlier fuel filter changes are not a big problem. However, layups of three months or more with B20 fuel is another story.

Beware of B20 in Idle Vehicles

We see trucks fueling with this and running without issue. However, they are always working and never parked for an extended time.  RV’s, in most cases, are subject to extended periods of non-use.   This makes them extremely exposed to internal system damage should B20 fuel be present.

Apparently, the sustainable-farmed fuel is not so friendly to some seal materials and metallic compositions that may be found within the fuel system. Even the injectors can suffer corrosive damage if the solution sits there for an extended period of time.

Biodiesel can be found in many states. The retailers are offered incentives to handle and sell it.  B20, for example, may have a substantial tax rebate compared to regular fuel.  This has driven fuel retailers to sell these higher percentage biofuels to offer lower prices and increase their profits.  In some areas it may be impossible to avoid having to use it.

Beware of B20 at the Pump

My personal advice is to avoid B20 totally. If that is all there is, dispense only what you need and reach a station that offers B-5 or less.

So, check what your engine manufacturer recommends as acceptable fuel and do your homework. Then you can make your own decision.

Peter Mercer–A Fuel’ish Idea

Leave a Reply


  1. Peter Mercer

    I am glad the bio-diesel fuels work well for your truck engines. However, some of the foreign made products, Mercedes for example, warn against using any bio that exceeds 5% (B5). Further more they state that damage caused by fuels that contain higher levels of bio, will not be covered under their warranty policy. That being said, it would certainly be in the best interest of such vehicle owners to heed the advice. Additionally, the RV application differs from your truck fleet in regards to duty frequency. RV’s are typically stored for a period of time annually. The time frame usually exceeds three months substantially. Cummins, though B-20 fuel approved, warn not to store their equipment over ninety days with B-20 fuel in the tank. So regardless of the industry’s conflicting ideas, it probably is best to follow the manufacturer’s recommendations.
    Thank you for your interesting comment and for taking the time to share your experiences.

  2. Anonymous

    We have used B100 in all our trucks for nearly 11 years; some with over 400K miles on them and other than filters we have never replaced a single fuel system part in any of them. On another point, I took a 55 gallon drum of B100 to my farm and used the entire drum in my JD tractor. The fuel had been sitting in the shop for nearly 3 years and it looked as if it was just produced.
    It has been my experience that most of the “expert” statements make about biodiesel could be considered weapons grade BS. We have found it to be an excellent fuel.

  3. Peter Mercer

    It is not just older diesels that are affected by the use of B20 bio-diesel. All European diesels are only designed to operate on a maximum of 5%, B05. Additionally all diesels, including Cummins engines, advise against storing a unit for over 3 months with B20 throughout the tank and engine. Well, storage of 3 months or more is quite usual for such applications as recreational vehicles. Thank you for bring this to our attention and for taking the time to comment.

  4. Anonymous

    Minnesota just raised the Bio blend to B20 as of July 1, 2018. What I have found is that the B20 is a fuel that can be used as a fuel. However, the engine or older engines have many problems that will come about if a raised amount of blend is above 5%. But the problem is that Minnesota mandated the B20 blend, which should put old diesel owners on notice. I own a 06 Duramax and GM has stated to me not to fuel the truck with any fuel above the 5% or engine damage will result. 07/26/2018

  5. Peter Mercer

    Well, it is great that biodiesel works well for you. However, your F250 probably gets regular use, that is it is not stored for long periods of time. Biodiesel blends of 20% are not recommended for storing of the vehicle for more than 3 months. For most motor homes, that is an issue.
    Thank you for your valued input on this topic, your participation is appreciated.

  6. Anonymous

    My personal experience is that biodiesel works extremely well. I’ve been running B99 Spring through Fall and B20 in the Winter on my 2005 6.0 Ford F250 with great success and no problems. I replaced the fuel filters after the first tank and now every 6 months, even though they don’t show any signs of clogging. One advantage is that I no longer need to use additives with the biodiesel as problems like stiction are a thing of the past. I’ve tested for oil dilution as well and with standard oil changes it isn’t any worse than regular diesel.

  7. Anonymous

    almost all diesel sold at any pump is a blend of up to 10% bio anyway, oil companies are allowed to supply this before it has to be declared to the end user, so anyone purchasing diesel fuel is using B1 to B10 anyway.