Whether you are driving a truck pulling a trailer or a motorhome with a “toad”, there are some things you can do to improve your fuel efficiency or miles per gallon (mpg). Small items we typically take for granted such as tires, maintenance, and driving characteristics can all make a difference.
Proper Tire Pressure
The pounds per square inch (psi) stamped on the side of your tire is maximum psi at its maximum weight which is not necessarily the proper tire pressure. Proper tire inflation can only be factored in by weighing the coach to determine what the actual weight is on the tires. Most large motorhomes’ 5th wheels have a cargo carrying capacity (CCC) of several thousand pounds and may not be even close to the maximum weight rating or Gross Vehicle Weight Rating (GVWR). The only way to verify proper tire inflation is to weigh the rig by individual wheel position and go to the tire inflation chart for your brand of tire. These can be found at www.rvsafety.com.
The Recreational Vehicle Safety And Education Foundation (RVSEF) has been weighing coaches for almost 30 years and recently recommended that smaller trailers should use the psi listed on the tire as they are relatively close to GVWR. Proper tire inflation provides the appropriate amount of tread on the road.
For example, the new Faulken tires on my 2016 Silverado read 51 psi at a maximum load of 2,601 lbs. The tire sticker inside the door shows 35 psi. The tire dealer recommended 42 psi and on a recent trip to Colorado, the truck bounced and banged all the way through Nebraska! I adjusted the pressure down to 34 psi and what a difference.
Overinflation will not reduce mpg however underinflation will as it causes additional resistance of the tread to the road surface. According to RVSEF over 50% of RVs they have weighed have underinflated tires. Their weighing teams have been conducting individual wheel position weighing at Rallies, dealerships, and special events for over 30 years. Underinflated tires not only cause premature tread wear and the potential for blown tires, but the resistance will also affect fuel economy.
Gross Vehicle Weight Rating
The Gross Vehicle Weight Rating (GVWR) is the maximum your rig can weigh with all the cargo, water, and LP. With motorized RVs, the GVWR also includes the people inside the rig as you will be in it while driving. The more weight you are driving down the road, the harder the engine has to work which means lower fuel efficiency.
I have driven several units on a gas rig and did notice a difference when towing a car or having the unit full of cargo and people. On trips to Colorado, a 36-foot motorhome with very little cargo and only two people got 8-9 mpg and one that was loaded got around 6-7 mpg! This is something that you will need to try with your rig and the power of your engine. A gas engine towing the same weight will get substantially less mpg than a diesel however the diesel fuel will typically cost more.
Although this may not seem like something that would affect fuel efficiency, not doing regular maintenance can lead to dirty filters that restrict airflow causing the engine works harder than normal. Make sure all engine filters have been changed to specifications and fluids are up to date as well. This also means checking the axles and wheels on trailers and getting the bearings repacked as recommended. Most trucks today have sealed bearings in a complete hub and can not be lubricated however, your trailer bearings typically can. Make sure you do annual maintenance on the trailer bearings and brakes. Most axle manufacturers recommend repacking and inspecting the bearings once a year or every 15,000 miles.
Another factor that can impact your mpg is the brake drum and tire. When I owned a trucking company, I would have my drivers use an infrared laser thermometer to record temperatures of the hub, brake drum, and tire every time they stopped for fuel. Extremely hot temperatures were an indicator of bearings getting dry or brakes set to high which could cause a failure, but we also noticed it affected fuel economy as well.
Keep in mind you are basically driving a “Billboard” down the road and winds, especially strong headwinds will affect your fuel economy. Try to avoid wind if possible, some RVers pull over and relax during windy conditions and wait for a more enjoyable driving experience.
Several highway studies have shown that driving between 55-65 mph will provide the best fuel economy and also staying at a consistent speed helps as well. How and when you drive can also affect fuel economy. The more traffic you find means the more fluctuation of speeds you will encounter and affect fuel economy as well. If possible, plan your trips for times with less traffic or reroute to avoid high traffic such as big city driving or mountains.
My truck is designed for “FlexFuel” so I can choose to run Premium, Super Unleaded, or E85. I typically run Super Unleaded at 87 Octane and tried Premium during one of my trips and did not see any difference in fuel economy.
However, when Super Unleaded hit the $4.79 mark one of our local fuel stations had E85 for $2.99 so I tried a couple of tanks and my fuel economy dropped by 4-5 mpg! Saving $1.80 per gallon did still make financial sense, but now that Super Unleaded is down to $3.49 and E85 went up to $3.29 it doesn’t make sense. I have also tried Seafoam as well as several other fuel saver products and did not see any difference.
About the author: Dave Solberg: Managing Editor, RV Repair Club
For the last 25 years, Dave has conducted RV maintenance and safety seminars, developed dealer and owner training programs, written RV safety and handyman articles authored an RV handbook reference guide, and logged over 100,000 miles on the road in an RV.
RV Repair Club is your go-to online resource for enthusiasts who want quality RV maintenance, repair, and upgrade information – a community where passionate RVers can come together to gather knowledge and share their experiences.
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Gary Oaks said:
Tried e85 once, never again. Pulling a travel trailer and almost killed the poor truck. No power for climbing hills.