My fuel mileage in my '02 GMC D/A has suddenly gotten worse, but only by one or two MPG. I wonder if it has anything to do with the new lower sulphur diesel fuel that is coming out.:(

Check for diesel in your oil. Might be an injector problem.

Good idea, and thank God for the 200,000 mile warranty on injectors......

When was your fuel filter changed ? Should be every 15,000 miles. You might of gotten some bad fuel or crap sitting on the bottom of the stations tank.

I just had the fuel filter changed about 2000 miles ago in preparation for my vacation. I didn't see any traces of fuel on the dipstick, so will keep an eye on things.

Mine has started to do the same thing but it is now starting to get a loud clack at idle speed. Will needing a ffuel filter change cause the loud clacking noise? I know it can pull my mileage down.

Also, will you ALWAYS get smoke when you have bad injectors? I have noticed that my truck actually black smokes pretty good when I hit it but not at any other time. I will check for fuel in the oil in the morning.

I checked the mileage on Monday and the high miles per gallon have returned! I am relieved....:cool2:

Mine has started to do the same thing but it is now starting to get a loud clack at idle speed. Will needing a ffuel filter change cause the loud clacking noise? I know it can pull my mileage down.

Also, will you ALWAYS get smoke when you have bad injectors? I have noticed that my truck actually black smokes pretty good when I hit it but not at any other time. I will check for fuel in the oil in the morning.

black smoke is ok (good if you like that kind of thing which i do):h ) white smoke is bad.

my truck never smoked when my injectors went

my millage is down as well