97 Gtp Bad Gas Mpg

[crazykid2145]

Hello....i have a 97 gtp and i am getting around 10mpg city and around 17 highway(I was usually getting around 17-28mpg)...i just recently yesterday changed my air filter and have saw the same mpg....there is no check engine light and i have recently changed the oil about 500 miles ago with my usual synthetic...it is very cold her but still i dont think that would affect it that bad and this has been going on for about 3 weeks....any ideas on what it could possibly be?

[grandprixgtx00]

how many miles are on the car? what kind of gas do you run in the car?

also...how long has it been since a tune-up??

[crazykid2145]

Recent tune up in the fall...yes have been running premium from bp 91 and its around 106K i have never had this problem before

[grandprixgtx00]

when the tune up was done...was the fuel filter changed??

[crazykid2145]

I believe so i would have to look at the receipt but it was around october and a auto shop so professionally done not by me

[Burtnette]

It's a curse in the gas/weather I'm telling you... I've heard literally 20 people mention their bad gas milage since winter started with me being one of them. Around mid Nov and right after getting my u-bend removed my gas milage suddenly dropped from 19-20 city to 16 city. And after my other mods it's down to about 13, 14 on a good day. Just wait it out till the weather warms up and the gas is deoxygenated or whatever.

[crazykid2145]

ya my car buff friend said the air/fuel mix is going to be more fuel in the cold winter so i figured but i just wanted to see if anyone knew it was something else but i am running a 3.4 pully so that is most likely helping in my MPG killing but thanks for your help

[Burtnette]

Originally Posted by crazykid2145

ya my car buff friend said the air/fuel mix is going to be more fuel in the cold winter so i figured but i just wanted to see if anyone knew it was something else but i am running a 3.4 pully so that is most likely helping in my MPG killing but thanks for your help

If your car reacts like mine than yeah it is haha. That's when mine dropped around an extra 3 mpg, after I switched out my pulley.

[richtazz]

Your highway mileage is way too low even for winter fuel (unless you drive 85-90 mph). What brand parts did they install when your tune-up was done, hopefully not Bosch!

I would check fuel pressure first, as it could be a fuel pump going south on you. Low fuel pressure is a common cause of bad mileage on GTP's.

If the fuel pressure checks out, I would do a vacuum test and/or exhaust back pressure test to see if you have a blocked converter.

[Hurtin97GPSE]

Full tank of Gas I can get from Niagara Falls, Ontario to Potterville, Michigan and be "just" about empty. (QEW - 403 - 401 - 402 - I69 || approx 330 miles) Edit: Just thought I'd mention, I use Esso's highest octane gas when taking the trip to Illinois and then BP's Highest octane in Potterville for the rest of the way there.

But lately, my city driving has been kinda crappy also. Quarter tank of gas won't last me more than 3 days and I'm driving about 16 miles a day. Granted my car is regulated for Canadian Gasoline and hasn't been re-programmed for US standards yet.