MPG getting worse on Motorhome

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

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

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

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

Hi,

I got a check engine light when my oxygen sensor went out. Changing it improved the mileage, so did changing to 91 octane gas. Fuel injected systems have anti-knock sensors, and low quality fuel will cause the computer to make the fuel mixture rich and/or retard the timing, both will lower the fuel mileage. Perhaps the fuel injector cleaner fools the system to thinking it was higher octane fuel?

Anyway I figure the 91 octane fuel will cost about 5 percent more, but save my by using 10% less gas.

Good luck!

Fred.

PS: THe oxygen sensor is only about $50 and can be installed in your driveway. I used one made for the 96 F-350 with 460" engine, same as my 97 motorhome has. It fits fine, actually there are many vehicles that use that same oxygen sensor. The biggest difference between O2 sensors is the length of the wires and shape of the plug on the end.

Fred.

Fuel filter has nothing to do with mileage. All it does is filter the dirt out. Injector cleaner might help..There are many things that can cause a decrease in mileage. Quality of the fuel, wind, speed, load, engine wear, tire pressures. The difference you see is probably normal. You will never get the exact same mileage with every tank of fuel. When it drops to a consistent 6-7 mpg then you might have cause for alarm. Just drive it..

B.O.