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Squeezing the best mpg from a RV

As a senior citizen on fixed income and an ardent RVer, I am on a quest to gain the best milage from my RV. I have a 1997 Coachmen 23’ Catalina (class C) powered by a Ford V10 engine. I have taken care to have the engine, tires and vehicle well maintained and in tiptop condition and consistenly get about 10 -11 mpg. After talking with outhers about this engine and chasis, Ford E 350 @ 10500lbs gw, I am getting good mileage but I really want to try to improve it further. My current strategy is to reduce my road speed down to an optimum point to squeeze the very best mileage possible from the rig. I currently keep my speed at approx. 60 mph but am willing to reduce it further if I would get better mileage. So, what speed would you suggest? Since I am retired, I am normally not in any hurry to get anywhere if it will allow me to continue to use the RV.

I would not reduce speed much more, you’ll risk being rearended by an inattentive driver. And it wouldn’t make that much of a difference, anyway. 10,500+ lbs is hard to improve much, you’re doing what’s recommended. Make sure the tire pressures are measured when cold (sure you are). There are expensive engine modifications (cam, intake, and exhaust manifold) that might help a little, but you won’t likely save enough on gas to pay for them.

You are doing well with what you have. Don’t try any of the gimmicky things like air filters and what not. They will either not help or not help enough to recoup the purchase price in mpg difference. The only other option to improve mileage is to get a diesel rig, but those come with drawbacks of their own, mostly in repair expenses and what not. Diesel engines tend to be more expensive to repair and maintain than the Ford modular V10 you have, which is a very good, smooth, efficient, powerful engine.

If you want to get a little better mileage, cruise just above the shift point to overdrive. You need to have enough RPMs to avoid lugging, yet not enough to use too much gas. About 300 to 500 RPMs over the shift point should be fine. If you find the RV hunting for gears, you need to increase your speed. For me (Honda Accord), I get my best mileage at 55 MPH (~1800 RPM). Your RV is likely different, though.

If you have a large clutch fan on your engine I would swap it out for a “flex” fan. It will slightly improve your fuel economy but don’t expect much because you have a V-10. The flex fan will also make it quieter in the cab. All the previous comments are right on the mark especially the advice about the tire pressure.

Thank you for your comments and suggestions folks. I guess it was unrealistic to hope for a “silver bullet” solution but I thought I would give it a try. I am concerned about get rear-ended if I get too slow. Thought I would put up a slow moving vehicle sign or flashers to warn others.
thanks again.

I might look into one step past Missileman’s flex fan idea - I wonder if an electric fan setup might help some. You might check out some RV forums, but be warned that scammers sometimes pose as owners to advertise.

@Minnemike, have you seen the bumper sticker" “You may have the right of way, but I have a truck”? You won’t be rear-ended. Everyone except an 18-wheeler would lose in that match. And then they’d have to pay to fix your RV. Your RV is big, broad, and heavy. No worries. Unless you use that Mercedes-Benz cloaking device.

Texases brought up a very good point that I should have expounded on. The electric fan will also work in conjunction with the flex fan if you decide to do that. If you travel in the desert at all then having both would keep the engine from possibly overheating.

If you are getting 10 - 11 mpg from a 23 footer, I would say that is doing quite well. We owned a 26 foot Class C motorhome with a 460 Ford for about 10 years and a 25 footer with a Dodge 360 for a year before that and got about 8 - 9 mpg with both. Slowing to 55 will result in better fuel mileage and is not a dangerous thing to do in my view. We drove many freeway miles at 55 and never got rear ended and offended no one to where we would hear warning horns or got evil looks except one time when a guy in a Volvo tried to crowd us over; it did not work for him. Just stay in the right lane. There is nothing surprising about a motorhome going slower than the speed limit; it is practically expected. The minimum legal freeway speed is typically 45 so 55 is well over that. Motorhomes are quite visible and I believed early on that it was a very safe way to travel. We traveled almost 50,000 miles in motorhomes without a safety problem.

The only other thing you can donis add a secondary overdrive unit. However the cost involved would be tough to get back in mpg. You can see if any of the programmers out there can get more mpg out if a v10, but all and all as other have said i think it’s a loosing battle.

I think you are doing very well. What is the rpm at 60 mph, and 55 mph? Reducing speed will help reduce the substantial wind resistance due to your “big boxy” RV shape. But too slow a speed will just involve more downshifts, and staying in the highest gear as much as you can is a big factor too.

I’d go 55 to 60 on flat ground. Let the RV roll to higher speeds on the downslope. On the up slope let the speed decrease until you get down to about 50 mph, then allow a downshift and maintain speed until you reach the peak. After the peak it will flatten out and then you can pick up speed to reach your 55 to 60 cruising speed.

60 mph on the highway in an RV? I think I saw you recently. There were 40 cars lined up behind you, half of them trying to get to work and becoming enraged. You may be retired and not in a hurry to get anywhere, but the rest of us are not. Show some consideration for the rest of us. Make saving a life more important than saving a gallon. Keep up with the flow.

If you cannot keep up with traffic and still get the mileage you desire, perhaps you should get a smaller RV. Meanwhile, stay off the highways.

I don’t mean to seem rude, but the attitude of “I’m in no hurry, so how slow should I go with my RV” needs to be challanged. It’s downright dangerous.

Uncle Turbo’s driving method is likely the best method to max out the mileage. Basically, don’t fight gravity with brakes, horse power and gasoline, try to take advantage of gravity. I grew up driving under powered milk trucks, school buses and far trucks and it becomes second nature to run like a roller coaster when you have no choice, but in your case it will mean a considerable savings.

And as for blocking traffic, mountainbke! I have a T-shirt monogrammed NO WHERE TO GO AND ALL DAY TO GET THERE for bicycle riding. But anytime I am moving slowly for whatever reason I pull over and let the working people go. Must of us “seasoned drivers” avoid heavy traffic. Rush hour is for people in a RUSH.

Point made Rod, I’d e interested in hearing the OP’s response.

There are still lots of places where the interstate speed limit is 65. If so, then 60 is ok.

But for lots of open road travel, its true that one will often be on roads with 70mph or higher. In that case, it is true that one becomes a traffic hazard. If I don’t want to go past about 60 for any reason I just don’t take an interstate. Most of them are built right next to alternate routes. Of course, we don’t know if the OP is on interstates or not.

As for the MPG, just try to always drive it downhill.

@Untcle Turbo… You have brought up another aspect dealing with the areodynamics (sp?) of a Class C RV. I have thought that the bunk over the cab has got to catch a lot of wind and make the engine work harder. In one of my “bog dreams” I have created an airfoil extending out from the front bumper which would deflect the air stream over and around the RV. It would be interesting to test the design on a virtual air stream measuring device sometime.
@ the same mountainbike… I appreciate what you say about slowing down the traffic flow and I am always considerate of the other drivers. I would adjust my speed according to the traffic flow. However, the majority of my driving is on lightly traved highways or on multilane where I can move off to the slow lane on the right.

Minnemike, that’s good to hear. And I appreciate your having taken my reply as a cry to focus on safety, consideration being one of the single most critical prerequisites. I apologize for the attitude of my post. I’ve simply seen way too many RVs leisurely rolling down busy roads and causing unsafe conditions.

I think you’r eon the right track making sure the mechanicals are in order and focusing on serodynamics. Remember the vehicle’s rearend too. The ability of the air to rejoin after the vehicle flows through it is also critiical to eliminating resistance.

Wing resistance is measured typically in a wind tunnel using 1/4 scale models. Wind tunnels capable of testing a full size vehicle are rare and expensive to operate. Perhaps in your case you could find a reasonably sized model of your RV, perhaps by contacting the manufacturer or even via an internet search. You could run a small fan through a clear plastic tube (perhaps from a large diameter animal run) and use an incense stick to let smoke in the inlet. That way you could play with aero add on ideas.

Only so much you can do with a rolling brick, it’s the cross-sectional area that’s also killing you, and that can’t be changed. It would need to be a BIG spoiler to affect the flow over the overcab area.