JNewvy

Just curious if anyone can help me. I have a '97 Grand Prix GT with about 125,000 miles on it. My gas mileage is now averaging about 13-15 MPG with about 80% city 20% highway. I just recently changed plugs and wires, air filter, alignment, tires, and struts(all 4). Even if I absolutely baby it, I still get horrible mileage. I wasn't sure if it could maybe be my fuel filter, I wasn't sure how much that affected it. It could be the original, I don't know, I haven't changed it since I got the car at 106,000 miles. I also can smell gas after periods of driving. Any help would be appreciated. Thanks

richtazz

Definitely change the fuel filter, and do you have a check engine light on? If so, get the car scanned (Auto Zone and Advance Auto do it for free if there's one in your area) and post the results.

JonJon68

Have you tried re-setting the MPG on your info center? Try it on the highway and see what you're getting. Replacing the fuel filter is always a good yearly maintenance idea especially with higher mileage cars.

JNewvy

No there's no check engine light or anything. The car runs pretty good, I mean as good as it can for the miles. And also I have reset the mileage on the info center. I've also done the mileage manualy atleast 6-10 times, and still no change. But I know I need to change the fuel filter so I think I'll do that when I change the oil. I'll let you guys no what I find out then. Thanks again.

BNaylor

Did you just recently start getting lower mileage? I've noticed colder weather during the winter months does affect mileage, especially in city. The reason why is warm up time takes longer so the PCM stays in open loop more often before it swtiches over to closed loop mode where it will rely more on emissions control and the two 02 sensors.

Another suggestion if you still have the original 02 sensors is to have the carbon cleaned off of each - one before the CAT and one after. It may help and depending on your mileage outright replacement resolves many fuel economy issues. Just be sure to use only the OEM AC Delco 02 sensors.

Another item that will affect fuel economy is the CAT convertor especially if there is an abrupt change in fuel economy with no other explanation or SES light including car appearing to run OK. CAT can be tested by running a low pressure backpressure test.

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'08 Pontiac Grand Prix GXP (Dark Slate Metallic) - LS4 5.3L V8
'08 Pontiac Grand Prix GXP (Liquid Silver Metallic) - LS4 5.3L V8
'02 Oldsmobile Alero GL2 - LA1 3400 V6
'99 Buick Regal LS - L36 Series II 3800 V6
'03 Honda CR250R MX - 2 Stroke 250cc
'97 Pontiac Grand Prix GTP - L67 Series II 3800 V6 Supercharged
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JNewvy

Thanks. I'll make sure and check all of those things out, cause you know it really sucks driving a Grand Prix and getting the fuel mileage of a Hummer you know.

richtazz

If you took the words "the fuel mileage of" out of that sentence it would be a GOOD thing, as long as you don't crash,

JNewvy

Haha! That's a good one!