why does my gas mileage suck I have an 99 Oldsmobile i get the oil changed reg but cleaner in it?

Answer 1

Could be alot of things.... I would start with a full tuneup...including......
Oil and filter
Spark plugs and wires
Air Filter
Fuel filter
Distributer cap and rotor

Then scan your computer with an OBDII scanner...if the mileage is still bad it might be the oxygen sensors.... I replaced everything on my 98 blazer and the check engine light was off and no codes.... I changed all 3 O2 sensors and that did the trick.

Answer 2

Too vauge of a question, dirty oil has nothing to do with gas mileage (actually if anything used oil is thinner than new oil and gives a little bit more gas mileage).

If it's not running rough or anything then it's probally just winter doing it to you.

Answer 3

The second answer; check all. Also check the air filter, pvc valve, fuel filter. Or maybe just needs a tune up.If you have A LOT of miles on the car that could be the cause also, AGE and how it's been driven.

Answer 4

a number of reasons, your spark plugs may be bad, you might need to change those to platinum or irridium, a new air filter will give you better gas mileage a air intake will give you better gas mileage and more horsepower, remember more power equals less gas...

Answer 5

check your driving habits.do a complete tune-up,like plugs,wires and clean the throttle body.also check the air filter,if its dirty,then it will use more gas.i have a 1988 olds delta 88 3.8 and i give mine a complete tune-up and mine is good on gas.

Answer 6

probable cause are clogged gas filter,weak fuel pump,sensors not responding quick enough,low engine compression,clogged exhaust system,carbon deposit build up inside the intake manifold,clogged injectors,and vacuum leak