MPG pathetic

wow.. are you serious? thats horrible. something is wrong there. very wrong. i just made a 900 mile trip home for thanksgiving and was getting from 105-115 miles to every quarter tank and i need to replace my o2 sensors.
 
If it's all highway then there is something worng. If you drive to the low fuel comes on at the VMM then you have about 3 gallon left so if you used 16 gallons that's about 12.5 miles per gallon. If you live where it's cold and you let the car idle to warm up and do a lot of intown driving it might be normal. Premium fuel doesn't get the same gas mileage as regular plus the fact that the SC is no lightweight contributes to it's bad fuel economy IMO. My 89 SC Auto get's around 250-275 miles on a tank in the summer. I have gotten 13 miles per gallon in the dead of winter before.

Keep the car in a good state of tune. Keep fresh plugs and wires in the car and if the O2s have never been changed then you might change them.

Tell us about your driving habits and climate where you are at.

Jerry
 
well i live in NJ and its cold , but I know its running rich, I did a burnout one day and it wheel hopped and a check engine light came on...

The car doesnt feel right at all, everyone can beat me in a race....

I should check the O2, maybe a wire got loose but can an O2 really affect it that much?
 
Have the codes read and see what code tripped the check engine light. It could be O2s or even a bad/dirty MAF. Not enough information to know until you at lest run codes.
 
Woa!!! I thought that was normal mileage :(. I always get about 50 miles per quarter tank of gas. This is with no o/d, but I got that on my old 89 SC manual as well. Hmm...I'll have to look into this.
 
On long highway trips, I can get over 400 miles to the tank which worked out to about 25-26mpg. Around town, I can usually get around 300 miles to the tank or about 18-20mpg.
 
I usually average 300-325 a tank on daily driving, about 20 mpg. If I take it on a long highway trip I get ~24, I usually drive 75 mph on highway trips.

When it is cold out, it drops to 18 mpg and 275-300 miles a tank.

1990 auto
 
In my 89 with AOD, I get about 475 to 495 miles on a tank of gas driving about 75 MPH.......Thats about 28 MPG

In the city though, it drops to about 18 MPG....
 
huh... I too always seem to get 15 MPG or less. I NEVER see the check engine light, except upon start up. My code scanner says all good. I just filled up today. 224 miles on 16.8 gallons. The best i have ever seen was before I blew the headgasket (12-02), and that was only about 21 MPG. Even if I never let it get into boost , it is still 15 MPG. Also, the difference between grandma driving (15mpg) and full boost, 4400 rpm shifts (12-13mpg) is small. can you tell by looking at the o2 sensors if they are bad? can they be bad without giving a CEL? thanks for help, and sorry I can't contribute any. :confused:
 
Generally O2 sensors are the culprit for excessive fuel consumption. If you have been driving it long that way then chances are the cats are also gone and might even be plugged. Yes O2 sensors are THAT important. I've seen cars with bad O2 sensors running as rich as 12.0 :1 AF at cruise and 9.0:1 on WOT. Normal is 14.7:1 and 11.5:1 respectively. If you've been running that rich then the 02's are probably badly fouled and in need of replacement even if that isn't the source of the problem. Check output of the ECT and ACT's also to make sure you don't have a problem with one of these. And no, they won't always set a check engine light.

Any decent SC should average over 300miles/tank. In the winter in NE Ohio I generally get right around 20mpg with a stock SC and have seen anywhere from 24-28mpg on the highway in the summer.
 
I have gotten almost 30mpg an the highway before...but back to his question..
Something isn't right Ed, Have you ran codes? If the CEL came on it might have stored some codes..
 
Where exactly are these 02 sensors and how does one go about checking them? Is it simply visually looking it over or is it more than that? Also, whats the ECT and ACT? Sorry for the n00b questions, but you have to start somewhere.
 
Randle said:
Where exactly are these 02 sensors and how does one go about checking them? Is it simply visually looking it over or is it more than that? Also, whats the ECT and ACT? Sorry for the n00b questions, but you have to start somewhere.
Click to expand...
No such thing as a dumb question except the ones you don't ask. :) Not sure what year you have, might want to edit your signature to show that, but on my 1990 SC:
There's an O2 Sensor on the passenger side exhaust manifold (look from under car) and another drivers side on the exhaust pipe just after the exhaust manifold.
ECT - Electronic Coolant Temperature Sensor is next to the DIS Module and where the fuel lines cross over to motor.
ACT - Air Charge Temperature Sensor is located on the return plenum. You'll see that standing at the drivers side fender looking at the back of the plenum. Should be the only sensor going into the plenum.
 
How can you check an O2(or O2's) to see if its working ok or not? I have spent lots of time with a shops hand held SNAP ON diagnostics CPU and the O2's are always switching. The 2 mechanics says thats what they do at idle. I'm in the same boat here, bad gas mileage. But no real "mechanical" issues. No codes have come up in a while now.
 
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