bad gas mileage!!!

[crazy9ceguy]

how come my friends car gets better gas mielage then my car? he has a s13 redtop, and so do it, accept his is a s13 hatch and mine is a s14 coupe. my gas needle also moves alot, like when im on the freeway it moves up, but when i get off and drive on the streets it goes down dramatically? the last owner changed the fuel filter already. would i need to change my ngk spark plugs? miles are unknown. what else can cause bad gas mileage.

[crazy9ceguy]

i am getting like 11 mpg, or so the needle says, i dont even know anymore

[Demik]

i am getting like 11 mpg, or so the needle says, i dont even know anymore


O2 sensor maybe...

[crazy9ceguy]

how do i know if an o2 sensor is bad? where can i get another one? and howm uch does it go for?

[Maeda]

Pull the plug on the manifold o2 sensor and see if it runs any different.
If it doesn't its bad. They're expensive usually.

[crazy9ceguy]

u mean i should notice the difference at idle? also my last 2 coilpacks are loose because the bolts broke off on the valve cover.

[misnomer]

wait wait stop.

NEVER calculate your gas mileage from the needle, it's way too innacurate.

Do this:

Fill your tank, reset your odometer
Drive around untill your tank is low
Refill your tank

Divide the miles on the odometer by the ammount of gas you bought.

THIS is your true mileage. Get that, and then go on to troubleshoot.

Now, a lot of mechanicals will effect mileage, but in my experience none of those (unless something is seriously wrong) will be as big an impact as driving style. On my KA, I have clocked ~23mpg on one tank of gas, and 30 on the next. Reason is the first tank was driving around the city and the second was cruising on the highway. If I drove harder in town, that could drop by another 5mpg. . . maybe more.

One other thing to keep in mind is modifications- the more power an engine puts out typically the lower it's gas mileage.

[Demik]

nicely stated misnomer

[Ski]

Yea, but driving style is not going to drop your mpg from 20+ to 11. If it were my car I'd try the O2 sensor as suggested or the fuel injectors. Are there any other symptoms your car is having? Is it buring through oil? Is the smoke coming out your exhaust discolored? I had a similar problem on a Jeep I owned. It ended up the head was letting oil into the valves. Give us more info.

SKI