MPG getting worse on Motorhome

[Public_Guardian]

Hi-I have a 1997 22'Shasta Ford E-350 chassis with V-10 triton engine. Class C with over 100,000 miles.

The rig was pretty consistently getting 10MPG. About a year or more ago the MPG dropped to about 8.5 MPG. When I changed the fuel filter the MPG went back up to 10MPG again. Over time the MPG dropped again so I put in injector cleaner and again the MPG went back to 10. Lately, changing the fuel filter does not make much of a difference to MPG. Putting the injector cleaner in still raises it back to 10MPG but the MPG drops down once the injector cleaner is out.I put in a new air filter during this time and had the spark plugs changed out. Neither seems to have had any effect on the MPG situation. Anybody have an idea of the cause consistent with the above facts. I assume it is in the tank-lines-injectors somewhere. All help is appreciated. Dennis

[MEXICOWANDERER]

Write your congressmen. Tell him you DEMAND a refund for the lost 1.5 miles per gallon. They accepted BRIBES from the corn lobby to mandate the garbage into the gasoline, so share with them the pain.

Wanna know how EVIL the corn lobby is? They tried coming down here and sell corn syrup to the soft drink industry at 40% of the dollar cost that US soft drink manufacturers pay for corn syrup. Once the sugar cane industry goes bankrupt they will jack the price way the hell and gone up. The Mexicans kicked them out of the country.

Enjoy paying nine dollars a pound for beef? It's all going out your tailpipe.

[wa8yxm]

Fuel filter can affect millage, if it's dirty and partially clogged the engine will alternate between starved and rich as the computer makes adustments, Not a good thing, That said it is fairly far down the check list.

Spark plugs, and their wires, timing sensors. Injectors epically if you buy cheap fuel, and a host of other things come first.. Even if there is no error code a professional reader may find out a few things or one of the real-time engine monitors.

I had rodent damage to some wires... I was able to tell the engine was mis-firing but my wife could not (Chevy V8) If Id have had a Ford V-10 I'm not sure even I'd have heard the misfire.

[JaxDad]

John&Joey wrote:
As a sidebar, V10 came out in 98/99, you said you have a 97 isn't that really a 460 V8?

They started putting the V10 in E-series vans for the 1997 model year.

[rockhillmanor]

Public Guardian wrote:
Hi-I have a 1997 22'Shasta Ford E-350 chassis with V-10 triton engine. Class C with over 100,000 miles.

The rig was pretty consistently getting 10MPG. About a year or more ago the MPG dropped to about 8.5 MPG. When I changed the fuel filter the MPG went back up to 10MPG again. Over time the MPG dropped again so I put in injector cleaner and again the MPG went back to 10. Lately, changing the fuel filter does not make much of a difference to MPG. Putting the injector cleaner in still raises it back to 10MPG but the MPG drops down once the injector cleaner is out.I put in a new air filter during this time and had the spark plugs changed out. Neither seems to have had any effect on the MPG situation. Anybody have an idea of the cause consistent with the above facts. I assume it is in the tank-lines-injectors somewhere. All help is appreciated. Dennis

Are you noticing any loss of power performance after you are on the road for awhile or up hill?

Bad fuel pumps are 'notorious' on the that chassis and the E450.

I had them replace fuel filter after fuel filter and even an expensive computer dodad until I brought it to a Ford Dealer and they checked the pressure of the fuel pump.

First I had a drop in mpg. Then the longer I drove the worse it got. Morning would be fine, but by noon it wasn't. They said fuel pumps don't just go out like in the old days. They start to fail and as it heats up performance/pressure drops.

It's a simple check and inexpensive to have it done. I would highly suggest you have the fuel pump checked out. A bad fuel pump can cause all types of different problems that none of the service shops I had to stop in seemed to understand. 😞 Ford dealership knew right away it was related to the fuel pump because they see a ton of them.

Since then I only use a Ford Dealership for all repairs and problems on my MH. In the long run it's much cheaper than using small repair shops.

AND a fuel pump going bad WILL affect your mpg just like a clogged filter will. Your engine is not getting the appropriate amount of fuel upon acceleration etc.

[John_Joey]

So how many years has ethanol been in our gas? How many BTU's of energy do you think they pack in 2.5 oz of injector cleaner.

IMO the problem with ethanol is it gums up after about 8 weeks. So the real question is in 8 weeks how many tanks of fuel does the average MH burn up. Most Class A's I see the weeds are pretty tall around them so I'm guessing none. In that light, if MH don't get used that often what do you think the fuel tank look like (crud, rust, etc...) might explain the filters needing to be changed often.

When I was lucky enough to find non-ethanol gas my F53 would only get a slight increase in MPG. What I did notice was the power I had when going up hills pulling a car.

To the OP, run the correct ratio of SeaFoam to gas (at least 1/2 tank worth), then change the filter. After that see if you're back to normal or not.

[rockhillmanor]

John&Joey wrote:
.... As a sidebar, V10 came out in 98/99, you said you have a 97 isn't that really a 460 V8?

I had a 97 and it had a Triton V-10.

[JaxDad]

robatthelake wrote:
I have a theory! I am of the opinion that all the Fuel Gas and Diesel contains fewer BTU 's than it did Five Years ago!!

Gas, yes, diesel not so much. The culprit is called Ethanol.

It doesn't contain nearly as many BTU's as gasoline does.

E15 gasoline only has about 82-85% of the BTU's (amount of potential energy) that gas used to have. If you lose 15% of the available energy! you also lose 15% of the work it will do and so use 15% more fuel to do the same work.

15% of 10 mpg is 1.5 mpg, about what you're losing.

The bump up is the higher energy in the injector cleaner.

[John_Joey]

Don't rule out the fuel filter as a cause. Go for a run, then place your hand over your nose and mouth and try to run again. Fuel filter works the same way. The PSI at the pump might be good but drops at the filter starving the injectors.

On my 96 I would change the filter yearly and always would store the gas if over two months with SeaFoam. I could always tell when the injectors would clear up on a cross country trip. It took a few days, but all of a sudden the old gal would pick up her heels.

As a sidebar, V10 came out in 98/99, you said you have a 97 isn't that really a 460 V8?

[badboy368]

VERY bad fuel theses days. Find a good fuel additive and use it all the time. I use SHAFFERS in my everyday car and it is very consistant 2-3mpg better over when i dont use it. It is just a poor quality fuel issue and your onboard computer is puting more fuel in it to run 😞

[robatthelake]

I have a theory! I am of the opinion that all the Fuel Gas and Diesel contains fewer BTU 's than it did Five Years ago!

I got 10.5 MPG 5 Years ago now I'm getting 7.5 ! Same Long Trips Fewer MPG and there is No change in My driving Habits or Payload!

[Public_Guardian]

I don't see the logic of some of the replies. First the 10 MPG has been consistent over more than 14 years with maybe a plus or minus 0.5 MPG due to change of conditions e.g. speed, wind, hills etc. Second if it were conditions, spark plug wires, 02 sensor, etc-why does it get better when the filter was changed or when injector cleaner is added? I agree that the filter should not change the MPG but it did. DES

[MickD]

You didn't say that you replaced the spark plug wires. They and the coil can be a source of lower MPG.

[Supercharged]

Number one reason is wind, number two reason is wind. on and on. Number 22 reason is wind.

[ScottG]

Replace 02 sensor even if it doesn't trip a code. They get lazy and don't change quickly after a while.