I have a 1998 GMC 1500 that I just purchased a few months ago and I'm starting to like it - maybe I won't get an F250 turbo diesel afterall...
Anyway, biggest problem I've got is my mileage, I'm not sure this is right. It's a 1998 GMC with the 5.7L and I'm getting 12.0 mpg back and forth to work. This mileage does not vary with driving styles or whether or not I warm it up before going to work or leaving work. Is this normal? Sorry for the newb questions but I know nothing about GMC and Chevy in general.
I've done nothing and looked at nothing since picking up the truck. I'm thinking maybe taking a look at the O2 sensors, spark plugs and wires. What are the tried and true brands for the above? Anything that's common that might cause poor performance? This is supposed to be my tow vehicle, should I be worried at all?

 

Yeah to be honest i have a 1997 Sierra and i get 12 Miles to the gallon. My truck has 424,000 Miles on it and it still can tow some stuff. You should have no problem at all.

 

Damn! your not joking with that "more miles than god". You have REALLY took good care of your truck, havent you...what year is it?

 

My friend has a 98 w/ the 350, gets about 14, so that may be right. At that age, may need to replace what you mentioned, but a visual check would suffice for the wires/plugs I would think, and the OBD should give you an error if there's a problemw/ the o2 sensor (up or down). As far as towing, he tows a 16 ft center console, and she performs beautifully. GMC has always been good for that (my '02 1/2 ton does fine w/ 5,000 lbs). Hope that helps...

 

yeah my truck is a 97. Yeah i took care of the thing as best as i can. its had some work done to it but nothing major to the engine.

 

ive known those trucks to get as low as 9 and as high as 15