Drop in mpg

[wthibeaux]

Hello all,
My truck is a 2005 Chevrolet 1500 crew cab with 5.3L engine, auto trans, and 3.73 rear end.
From day one, I got over 19 mpg solo at mostly highway speeds.
Recently the mpg has dropped to the high 16's and low 17's.
It seems to run as well as it always has, no missing or sputtering.
The air filter has been checked and is ok. My mechanic says the fuel filter is in the gas tank and does not require service.
I have heard everything from a lazy oxygen sensor to the MAF maybe needing cleaned.
Does anyone have any ideas?
Thanks, Warren

[CD]

wthibeaux
I don't know how this would apply to newer vehicles but years ago when my milage would drop off with no noticable lack in oerfomance, I would tune it up (spark plugs , points etc) and the milage would be back.

[denochs]

If it has fuel injectors try using some type of cleaner for them first. I had a similar problem with a 7.3 diesel and two tanks of treated fuel brought the mileage back up.

[thepratts]

I am not trying to start arguments so please take this as my personal experience only. MY motorhome milage has dropped about .5 to 1 MPG in the last year or so (down to 6.5). I have read that much of this is due to the increased use of ethonal. It is up to about 10% in our area. The milage on our cars has also dropped. Your drop sounds about normal for the increase in ethonal. Ethonal works very well in high compression engines designed for it. Our normal gas engines are designed for gasoline.

[Half Dimes]

Quote:

Originally Posted by thepratts I am not trying to start arguments so please take this as my personal experience only. MY motorhome milage has dropped about .5 to 1 MPG in the last year or so (down to 6.5). I have read that much of this is due to the increased use of ethonal. It is up to about 10% in our area. The milage on our cars has also dropped. Your drop sounds about normal for the increase in ethonal. Ethonal works very well in high compression engines designed for it. Our normal gas engines are designed for gasoline.

I noted the same thing about a year ago when ethanol was introduced into gasoline in our area. Seems like 10% ethanol = 10% reduction in mileage. Noticed a similar effect on our old diesel truck when ULSD was introduced.

[Ray,IN]

I don't believe your mechanic told you straight. The fuel filter should be changed per maintenance schedule OR whenever performance decreases.Try running a quality fuel system cleaner for a tankful. Seafoam is just one such product.