Questionhi alicia, i have a 2000 silverado with the 5.3, auto, air, 4x4, latley i have been noticing poor fuel economy. i have no black smoke, seems to perform well, no check engine lamp, i replaced the plugs about a year ago, the air and fuel filters about 4 months ago, the trans, diff, tansfer case, and engine oil levels are all good, tire pressures are good, brakes aren't dragging, not stuck in 4x4, i am running out of ideas as to what it would be, any advice would be awesome, thanks, mike.
Answera few things .... you said you replaced the plugs did you replace the wires? if not then do...
the throttle body maybe dirty have it cleaned
fuel injection system cleaned
distributor or coil and rotor be replaced...
depending on the mileage i highly recommend high mileage oil or synthetic i have a 1999 suburban with 126,000 miles and i use that... i have a 42 gallon tank on my truck and i get 650 per tank on half highway half city driving...
what happened to mine is that it seems to take more gas to get it going which in turn was causing the truck to use gas
i may be possible your truck is running lean getting air in somewhere.. cracks in the air intake components just getting to much air in will cause a drop in gas mileage and loss of power...
look also for leaks in the exhaust and a clogged catalytic converter
