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Ask Dave: Is there anything I can do to improve gas mileage?

Dear Dave,
Is there anything I can do to improve my gas mileage? —Randy, 2009 Winnie Outlook

Dear Randy,
There are several things you can do to improve gas mileage when pulling your Winnebago trailer down the road. Proper maintenance, tire pressure, and weight are the first things I would look at.

Proper maintenance will improve gas mileage

Since you have an Outlook and stated “gas” mileage I assume you are towing with a light-duty truck? Make sure all engine filters have been changed to specifications and fluids are up to date, as well. Most trucks today have sealed bearings in a complete hub and cannot be lubricated; however, your trailer bearings typically can be. 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.

I ran a company for the past ten years that had three trucks and trailers on the road towing more than 100,000 miles each. My drivers used 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 too high, which could cause a failure. But we also noticed it affected fuel economy, as well, due to the resistance.

How tire pressure affects gas mileage

According to the RV Safety & Education Foundation (RVSEF), more than 50 percent 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 more than 30 years. Underinflated tires not only cause premature tread wear and the potential for blown tires, but the resistance will also affect fuel economy.

Proper tire inflation on your trailer tires can be found on the sidewall of the tire. For your truck, typically the recommended pressure is on the data plate of the truck. The tire pressure on the sidewall of the tire is for maximum pressure at maximum weight. Typically you will not have the back end of your truck filled with that much weight. The new tires on my 2016 Silverado 1500 show 51 psi.

The tire sticker inside the door shows a different psi.

When pulling a trailer, I typically go to 40 psi, which seems to give me the best tread on the road.

Weight

Your trailer has a Gross Vehicle Weight Rating (GVWR), which is the maximum your rig can be loaded with everything including cargo, water, and LP. The lighter the load, the better gas mileage you will get. Make sure you get your rig weighed and find ways to lighten it by not carrying full water, which weighs 8.6 lbs. per gallon.

Also, make sure your tow vehicle matches the weight of your trailer. One year we purchased an F-250 with the Triton V10 that supposedly had a towing capacity of 11,000 lbs. Our trailers weighed about 8,000 lbs. We got  6 mpg with that truck and could barely get over a 6 percent grade. We got rid of that right away and went to diesel.

Driving characteristics that affect gas mileage

How and when you drive can also affect fuel economy. The faster you drive, the fewer mpg you will get. 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. Use a bypass option, if available.

Also, try to avoid wind, if possible. A strong headwind can cut fuel economy in half. I know several RVers that just pull over when they hit a strong headwind and relax for a while until it dies down. After all, they are not in a hurry as they are “recreating.” Plus, they don’t like fighting a headwind, either.

Fuel

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. I 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.

Over the road, truckers have been trying various deflectors underneath and on the back, but I have not seen anything that has been beneficial for aerodynamics on an RV. Maybe our readers have more tips they can share in the comments below. Readers?


 You might also enjoy this from Dave 

Why does diesel fuel cost more than gasoline?

Dear Dave,
Why does diesel fuel cost more than gasoline? —Don

Read Dave’s answer.


Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here

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Al H.
5 days ago

Having not yet filled my annual quota of “Hold my beer and watch this….” activities, I allowed myself to be sucked-in by an ad showing Elon Musk hawking a gadget that plugs into your vehicle’s computer port, and “doubles your fuel mileage!” Yeah, right. I ordered it just to reassure myself that the laws of physics haven’t been altered since I studied them 50 or so years ago. I’m sure my 8.1-liter Silverado will be impressed! If it does anything at all, I’ll let you know, but I expect that any improvement will be the result of the lightened load in my wallet!

Bob p
5 days ago
Reply to  Al H.

That gas saving device is just that, a device! I bought one just like it 2 years ago but not from Elon, the gas mileage improved until I forgot about it and started driving like I always did, then it dropped. In other words, when I was thinking about that device my driving habits improved saving gas, when I went back to driving like I normally do it fell off. Your right foot has more to do with economy than we want to admit. I’m now driving my first hybrid, and believe it or not, the cruise control and computer get better mpg than I can with my foot, and being a retired truck driver I know how to drive efficiently.

Geewhiz53
6 days ago

If your worried about what’s been the norm for RV’s for decades they suck gas and they’re not for the faint or low budget buyer. It will each a hole in your pocket and you should know this up front. If your upset with poor mileage maybe you shouldn’t have invested in that gas guzzler.

Bob
7 days ago

Yes, adjusting your speed is one of the best fuel saving practices. When I pull my TT, I try to keep my speed between 60 and 65. Above 65 I can see my mileage drop considerably. At 60mph my mileage is about 11mpg. Over 65 it drops to 8-9mpg. Doesn’t sound like much, but it’s an extra 60-70 miles with my 26 gallon tank.
I have a DIC in my truck and it shows estimated mpg. It is pretty accurate.

Jesse Crouse
7 days ago

Take your foot off the pedal. Just because you can go 70 to 85 mph doesn’t mean you should. My biggest business expense is getting to the various jobs scheduled for the day- Plumber. When RVing it’s 60 to 65 mph. I am on vacation and it is safer. We drive a 40 foot diesel pusher

Bob p
7 days ago

Best fuel saving, don’t start the engine! Seriously you covered most of the fuel saving ideas. E85 has 25% lower BTUs than 87 octane regular so you can expect 25% less mpg. Wind deflectors are only effective if they are within 3 feet of the front of the trailer, look at semis, their tractors and wind deflectors are very close to the trailer nose. When I was driving semis if my load weight required moving the 5th wheel back to far I could lose up to 1 mpg. To much gap will cause turbulence which causes poor mpg. Your speed is probably the biggest mpg eater, everything over 55 mph is causing poor mpg. I always towed at 62 mph, I wasn’t creating a “rolling roadblock” and my engine was right at the most efficient rpm and I could enjoy the scenery, remember it’s not just about the destination, but about the trip getting there.

Dave
7 days ago
Reply to  Bob p

Absolutely right. Towing above 62 mph kills gas mileage.

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