Should our RV be getting only 7 mpg?

Factual Questions
1

Hi all.

We have recently travel about 1000 miles cross country in an RV. Long story short is the gas mileage seems to be particulary bad on this trip. My SO swears back before my time on the scene the RV got something like 14 miles per gallon. And that was with towing a car, probably driving a bit faster, running the generator (and both the AC units that run off the generator) and smidge more stop and go traffic to boot.

THIS trip we are averaging more like 7.5 give or take. I’ve never bothered to keep track of our mileage on all the shorter (couple hundred miles tops) trips we do fairly frequently, so I don’t know whether this a new thing, a gradual thing, or my SO’s memory of the good ole’ days is just wrong.

One thing is different. We are now towing a Jeep Liberty with 2 canoes on top rather than in the ole’ days which was just a smaller more streamlined Saturn car without boats on top. But the Jeep and canoes still appear to me to be mostly in the “slipstream” behind the RV. I could see it increasing the drag a bit more than the old Saturn, but I can’t imagine it dropping the gas mileage by 50 percent.

The RV is a 35 foot class A motorhome. Model year 1997. It has the older “basements” so I supect it is not quite as tall (and therefore draggier) than newer models. It has 37,000 miles on it. The engine is a Chevrolet 454 7.4 liter V8 Vortec engine with SFI (which I guess is some sort of fuel injection system).

We are typically driving it in the 60 to 65 mile an hour range. We left from the south and are now in the midwest so its not like we are climbing mountains either. Its mostly been interstate or good highways so not lots of stop and go traffic either. If I assume worst case fuel consumption for the generator running full out (according the manual), the mileage is more like 8.5 miles per gallon.

So, given all this, is this the kind of mileage one would expect?

One thought I’ve given is to try a fuel injector cleaner before we head back in a few weeks. Any recommendations as to brand/type and hints on using it? Or is using it a BAD idea? Even if it helped just a bit on mileage it would probably pay for itself on this trip alone.

Any hints on what else to possibly look at? I could probably do the air filter, spark plugs, and spark plug wires myself before heading back. Maybe the generator is REALLY sucking gas?

thanks for any hints or input!

2

7.5-8.5 miles per gallon sounds about right.

A lot of large SUVs will get down to 14 mpg on the highway, and your RV is a lot larger than those.

3

you’re lucky to be getting 7.5, IMO.

4

http://www.rvmechanic.com/rv/motorhome/talk/current_category.181/Forum.55243/forum_thread_full.html

Seems about right.

5

That 454 is a big engine! From what I understand 10 MPG is pretty much standard for the fuel-injected big blocks, but that’s when they’re in empty pickups! With all the however many tons of RV goodies (and that 2-ton Liberty), I would agree with the others that 7.5 MPG is quite good.

6

Your mileage sounds about right. I did not see the gross vehicle weight, but that engine is not great for mileage. You may indeed have gotten more mileage in past years before they increased the amount of alcohol mixed with the gas. Everybody’s mileage went down. My pump says the maximum amount of alcohol is 10%. I bet it’s even more than it supposed to be. I think a lot of us are using E85 without knowing it and paying for pure gas or at least E90.

7

E85 is 85% ethanol
The stuff you buy at the pump would be E10.

I doubt that someone would be selling E85 as E10, and in many cars they are not able to run E85 at least without setting off the check engine light.

8

Thanks folks.

Sounds like the SO’s memory is faulty. And thinking about it, moving this much crap around and still getting mileage that “good” is surpising.

9

In conversations like this I always like to point out that Ms Hook and I get over 13 MPG when pulling our 12,000 lb 5th wheel.

On flat ground near sea level (I-5 in California) we generally run closer to 15 MPG.

10

7-8 mpg is really what you should expect from a 35ft AND tow at that speed. I have a 30ft '92 Fleetwood with the same engine, I’m not towing and get a little better mileage from an Allison transmission in overdrive (~12 mpg) under absolutely ideal conditions (no side wind, flat-ish road and 55mph.) Of course that’s an extra day off my vacation but heck - what’s the hurry?
Also when on the road my water tank is only 1/4 to 1/3 full. There’s plenty of water where I’m going, no need to add weight and I sure as hell won’t take a shower at the roadside turnout.

Oh and did I mention that I’m hypermiling whenever I have the chance.

11

You’re running a gas generator at the same time? You should be able to calculate how much fuel it burns an hour and add that back into to your fuel economy calculations.

12

That’s impressive. Is the tow vehicle a diesel? The OP’s mileage sounds about right to me. We pull a 5th-wheel+boat combo that weighs a little less than your fiver. I’ve yet to get 7 mpg. Usually 6-6.5. I suspect that some of the difference is due to friction of having 12-wheels in the ground, and that our rig as a whole is very un-aerodynamic (gaps betweeen truck/trailer, and trailer/boat). We’ve just had to accustom ourselves to the fact that a long weekend at a faraway lake will usually run us around 120 gallons of gas, when truck, boat and generator are all fed. But having the place to ourselves is worth it.:slight_smile:

On edit: The truck is a gasser.

13

Hi all.

Again guys thanks for the input. Sounds like things are just as they should be for us gas mileage wise. Oh, did you know they make sausage gravy dispensers? Like the ones you see at fast food places for fixing your own drink, but for gravy instead. This place had a dispenser that popped out a biscuit in a bowl. You then took that biscuit/bowl, peeled off the plastic covering, placed it under the gravy dispenser, pressed a button, and filled er up.

Wait until the Deep South hears about this modern marvel.

14

“hears about?” how in hell did the Deep South not invent this? It sounds like all kinds of awesome.

15

Yeah, personally I am a bit embarassed about that myself…We decided to take pictures and we were a bit afraid the folks in this middle of nowhere country “store” would take offense. But they were proud of it and even opened it up so we could see the magical inner workings. I told them I thought there would be like Kebler elves in there with a tiny stove tops and pots slaving away, but alas it just a kinda like a giant hospital IV bag except filled with sausage gravy. Some mysteries are better left unsolved I guess…

Anyhow, if you must know more, do an internet search for Bob Evans gravy dispenser. You can get one magical dispenser AND 4 cases of IV gravy for under $600. Apparently the Bob Evans company IS east of the Mississippi but I don’t know how southern it is. I just know I’ve never seen one of those contraptions down south. Then again I don’t get out much fast/junk/convience store food wise.

If I do win the lottery I will say I’ll buy one of these babies before I buy an expresso machine.

16

Bob Evanses are quite common in Michigan, so 'taint all that southern.

17

First the civil war, now THIS. Oh, its on now baby!

Oh, I started a thread in cafe society about this if anyone is interesed.

18

Late to the party on this one, as we’ve spent the last week on the road in the John Day area of Oregon. Our old RV was a 27’ Class ‘C’ with a Triton V-10. It got 8 mpg regardless of whether or not I was pulling a toad, uphill, downhill, etc. The marvels of metered fuel injection. My present RV is a Class B (van conversion), which gets about 12+ with a V-8, but that should improve over time, since I only have about 2,000 miles on it.

For me and my family, gravy is considered a beverage, so I’m all for a dispenser. In fact, I had thought about opening a gravy bar, much like an espresso stand, where I would dispense shots of one’s favorite fat-based substance. I was going to call it “One Foot In The Gravy”. Any potential investors may contact me via PM.

19

My in-laws had a huuuuuuuge RV which, when fully laden, was noted to be approaching the “gallons per mile” designation.

20

God, I love sausage gravy. If I had a motorhome, I’d have a sausage gravy dispenser in it.