RV Fuel gremlins — How RV environment impacts mpg. Part III in a series.
Environmental factors play a major role in altering our fuel consumption numbers. The biggest of these factors is wind. This can drop your expected fuel mileage substantially, or it can boost it to surreal levels. It all depends on the direction and speed.
The majority of motorhomes have a large frontal area and overall body. Wind challenges the aerodynamics of this greatly. A headwind of 20 mph can simulate the vehicle doing 80 mph when it’s actually traveling 60 mph. This will require substantially more power to maintain speed. A motorhome’s mpg will drop about 10 percent for every 10 mph of headwind.
On the good side of the coin, a tail wind of 20 mph will simulate an aerodynamic speed of only 40 when, in fact, you are travelling at 60. Your mpg will soar.
Crosswinds, even at 90 degrees, will also cause excess fuel burn, as this turbulence increases the tire heat and rolling resistance. This is due to the cramping of the front wheels to counter the side thrust. So, as roads are rarely only straight, winds are usually a negative when it comes to fuel mileage numbers.
RV Environmental Factors — the Heat is On
Temperatures also influence fuel consumption. Colder air is denser. This heavier air increases resistance adding to the aerodynamic drag. In fact, for every 10 degree. drop in temperature, aerodynamic drag increases about 2 percent. This in turn will result in about a 1 percent loss in mpg.
Winter weather travel generally consumes more fuel per mile than summer. The impact can be as much as 7 percent or 8 percent. There are several factors that account for this jump in consumption. Winter blended diesel fuel may help prevent jelling of the fuel, but at a loss of up to 3 percent of the fuel mileage. Winter temperature fluctuation additionally causes it to be difficult to maintain correct tire pressure, more precipitation increasing rolling resistance, wet cold conditions causing drive train components to run below their most efficient temperatures, and longer warm up and idling times.
So, as you can see, the seasons and the weather can have an adverse effect on your fuel expenses. They can also cause the unfortunate slip-up if your MPG is running lower than normal, causing you to unexpectedly run out of fuel. For situations like an empty fuel tank — as well as many other side-of-the-road breakdowns — a roadside assistance plan protects you from the especially costly RV tow. For example, Good Sam Roadside Assistance plans all offer emergency fuel and fluid services in the event of a fuel-related breakdown.
Last week in part 2 we examined “Wheel Factors.” Next week we will take a peak under the hood to unmask those components that consume fuel quietly in “Onboard Fuel Eaters.”
Peter Mercer — With a Fuel Saving View