Gas Mileage very low.

[steelerfan]

Hello all.

Long time user, first time post....er (hmm, right)

OK, a few weeks ago i bought a 95 green MTX with a very resonable milage count (77k). I live in Denver and so far i am enjoying my new ride. I am however noticeing a huge difference over the past couple tanks of gas i have gotten as far as mileage is concerned. I currently have traveled 100 miles and i am at a half of a tank.

any thoughts on this matter?

 

[fricker66]

Welcome to the forum. There is a lot of useful information/advice from the users.

As far as the fuel mileage....first off I'd make sure the gauge is working properly. Fill the tank back up and make sure it takes about half the capacity. If it is, there's a whole host of items that should be checked/replaced at the first 60k that can affect mileage. O2 sensors, spark plugs, etc. Also, proper tire inflation has a direct impact on the fuel mileage. Sorry I can't give you just one answer! Have you calculated the exact fuel mileage?

 

[steelerfan]

Yeah, so far I have gotten some great info from here and look forward to meeting some good people.

Tire pressure is good, that i know. The other stuff i will have to look into. It doesnt feel that i have any lose in power though (However this is my first time driving an SHO and my previous car was a saturn.) I will check out my plugs and o2 sensor. how do i check an o2 sensor?

 

[Mr Anonymous]

Double-check for items that would be likely to cause a too-rich fuel mixture condition.

My first step would be to check for any Diagnostic Trouble Codes that might indicate component issues leading to a rich mixture.

I'd also keep an eye on the dash temperature gauge. If it's indicating a cold condition (staying at or below the blue line) when the car has been driven for 10-15 minutes, you may have a thermostat that's stuck open and causing the EEC to think that the car is still cold and thus enrichening the mixture.

 

[twr]

Generally you don't check the 02 sensors (there are 2 on a 95') you just replace them - not to hard to do. Steeler Fan in Denver huh, must get a lot of static for that one. If you need any help or need any info feel free to email or PM me. We have a good group of guys in CSHOC, you are more than welcome to stop by one of the meetings if you like.

 

[steelerfan]

It is kinda tough Terry, but ya gotta do what ya gotta do. Grew up in Pittsburgh all my life and you can never get the "burgh out of the boy". What is even tougher is that fact that i am a Penn State grad and have to deal with The Buffalo's being in the Big 12.

Just to let you know Terry i emailed you earlier about the reverse grind that you helped me out with...thanks. And I am planning on meeting you guys on Nov. 14th.

I am fighting myself over maintenace or modifaction but i guess i should maintain (sp?)and set aside some dough for a partial 60k.

And, yes in fact, i have noticed it running cold. Maybe i could replace the o2 sensors, wires, plugs and thermostat.

Also i am wondering if altitude is coming into play here.

 

[TAM]

I had terrible milage and engine would kind of hunt around trying to idle for first few miles dropping to 500 RPM then dying occasionally also - again while warming up. Temperature gage seemed abnormally low also.

Was convinced thermostat was staying open all the time causing to rich a mixture so I had a new thermostat installed and stalling stopped immediately. Car has idled perfectly ever since.

Then I installed new cat converters from Sho Shop and new O2 sensors because car failed emmisions BIG and milage jumped from 12MPG to 16MPG in town with fairly heavy stop and go traffic.

<small>[ November 05, 2002, 02:11 PM: Message edited by: TAM ]</small>

 

[jelloslug]

I'm assuming its been colder there recently, I would check the thermostat. Mine seems to be stuck also and I have noticed a drop in MPG in the last few weeks with the temperature drop. Also I would not mod your car at all untill your sure its in tip top shape. The power gains I have gotten from just bringing it back to factory tune have been good so far and moding a car that has weak points will only make it break faster.

 

[hooterville]

Try performing a tune-up. You might need 02 sensors. Low/old oil will cause poor gas mileage. Poor air intake will cause poor gas mileage. Clogged cat will cause poor gas mileage. Is your CEL light coming on periodically? If it is, do a self check. It also might be a Throttle positioning sensor. Good Luck

 

[TAM]

Wires should be good for 120K unless you can find some damage. They ain't cheap!

 

[Lurch]

I have driven 97 miles on a full tank in my new-to-me 91 SHO MTX and my fuel gauge is just a tick above a half-tank. I just thought the gas mileage for these cars wasn't so great, but this sheds some light. I noticed that driving around last night (about 25 minutes, ambient temp. about 40 degrees F) that the temp. gauge didn't get off of the A in normal, and today on my way to school (about 5 minutes, 35 degrees F) the gauge never moved off of the blue. Thermostat would make sense, except that it was replaced (according to previous owner's records) about 3-4 years ago. Out of curiousity, how far do you other SHO guys get out of a tank of gas? Mid grade is in mine right now, might this affect mileage? I'm going premium from here on out I believe.

 

[fricker66]

I typically get around 350-400 miles per tank. That's with taking the gauge down to the 1/4 mark. A lot of the mileage depends on driving conditions/style. My SHO is my daily driver to work and obviously I don't get many WOT runs with the rush hour traffic!! Just keep an eye on the running condition and I'm sure you'll find any problems.

FWIW, when my 89 had a stuck t-stat, I was still getting 25 mpg on highway driving. Didn't notice any mileage problems, just never could get warm in the winter!

 

[Mike93]

I live in the city and am getting about 250 miles a tank, this is with about 10% highway driving. Best highway mileage was something in the neighborhood of 32-33 mpg. Can't remember for sure, this was last summer on a road trip.

Bought the car in June with 100K miles. Now at 106K, the only things I've done have been new O2 sensors and an oil change.

FWIW, my water temp gauge stays abnormally low but every so often it will climb into the NORMAL range.