Poor Gas Mileage?

[roadkilldave]

I have a 95 SC2 that I recently purchased and it's only getting 24 mpg. There is no SES light. I put new plugs and wires on it. It seems to run real good.

Any ideas on what is causes the poor mileage when no SES light is on?

Thanks!

[eric02SC2]

If the engine control unit (ECU or computer to the rest of us) thinks that the engine is cooler than it really is, the ECU runs in open loop mode which uses more fuel than closed loop mode.

The most likely cause of this is a defective Engine Coolent Temperature Sensor (ECTS). Up until 2001 or so, they were reson tipped, but the new design is brass tipped. That is what you want for a replacement. The old design was prone to cracking and corroding the connector (a dealer only part AFAIK).

Eric & Genieve
2002 SC2m 47.8k miles

www.gems-family.net

[rugevit]

My 94 SL2 has been getting poor MPG as well...its been getting about 25 or so and i been switching stuff on it to try and figure it out. So far the SES light isnt on at all..and i still have to clean the EGR and Throttle Body....but im also wondering if it could be head gasket as well thats causing the poor mileage seeing as though ive changed the ects and a few other parts which include the plugs and wires...coil packs and control module...O2 sensor and MAP sensor. Could it be something else possibly or is the head gasket a good candidate?

[BarnOwl]

The head gasket is pretty unlikely actually. Driving style has as much effect on mileage as anything else. If you don't know that the mileage was previously better with your driving style, that may be the problem.

[PeteB]

Cleaning the fuel injection system with a good cleaner such as Chevron Techron (highly regarded in the forum) can help a lot. Dirty injectors will often leak.

[dansl2]

Originally Posted by roadkilldave

I have a 95 SC2 that I recently purchased and it's only getting 24 mpg. There is no SES light. I put new plugs and wires on it. It seems to run real good.

Any ideas on what is causes the poor mileage when no SES light is on?

Thanks!

I'd bet on the ECTS making a difference. I recommend dealer on that item, but you can find aftermarket ones a little cheaper-be SURE they have the brass tip. Instructions (with pictures) on how to change it can be found in the "how to library".

PeteB, Check your tire pressure. Know it sounds like a joke, but it can make 3-4 mpg difference (depending on how low it is now).

[rugevit]

Originally Posted by BarnOwl

The head gasket is pretty unlikely actually. Driving style has as much effect on mileage as anything else. If you don't know that the mileage was previously better with your driving style, that may be the problem.

only got the car in november...165k miles on it...been working out bugs since...and thats one of the last resorts. Gonna have pressure checked on it before i do anything...but that is about the last option i can come up with. seeing as though i dont drive it all that hard.

Unless it may be the purge solenoid...but im not sure of the symptoms of a bad purge solenoid....anyone know what they are?

[PeteB]

Originally Posted by dansl2

PeteB, Check your tire pressure. Know it sounds like a joke, but it can make 3-4 mpg difference (depending on how low it is now).

Yes. I use 4 extra pounds all around. My mileage is OK for an automatic with iffy rings. I get 30 mpg mixed driving, and up to 36 highway.

[wolfman]

With winter blend fuel, COLD weather and remote start warm ups, my 97' SL2 automatic is down to 24~26 mpg 75% city....and there is not a thing "wrong" with it I assure you. When summertime rolls back around, I'll see 32 again I'm sure.

[adhhaahok]

hey PeteB. too much pressure is just as bad as not enough. when your pressure is too low, your tires wear on the outside at a higher rate, and when it is too high, they wear on the inside faster. both cause a decrease in gas mileage. the PSI recomendation on the tire will give you the slowest treadwear and highest gas mileage. go with that and you wont have a problem with your tires.

[Token]

Originally Posted by rugevit

My 94 SL2 has been getting poor MPG as well...its been getting about 25 or so and i been switching stuff on it to try and figure it out. So far the SES light isnt on at all..and i still have to clean the EGR and Throttle Body....

How do you clean the EGR?

[PeteB]

Originally Posted by adhhaahok

hey PeteB. too much pressure is just as bad as not enough. when your pressure is too low, your tires wear on the outside at a higher rate, and when it is too high, they wear on the inside faster. both cause a decrease in gas mileage. the PSI recomendation on the tire will give you the slowest treadwear and highest gas mileage. go with that and you wont have a problem with your tires.

Actually, higher pressure = lower rolling resistance = lower temperature, greater treadwear, better mileage.

It also gives less tire adhesion (which hasn't been a problem) and can cause more wear at the crown of the tires, so I'm keeping an eye on them. I think the stickers are probably for best tire grip. Mine says 30/26 but I use 34/30.

[rugevit]

Originally Posted by Token

How do you clean the EGR?

there are a few threads out there...

http://www.saturnfans.com/forums/sho...t=cleaning+egr

http://www.saturnfans.com/forums/sho...t=cleaning+egr

http://www.saturnfans.com/forums/sho...t=cleaning+egr


thats couple of em...and im sure some of the others know of a few more....

[Redbeard]

Is this a Saturn thing? Cuz I've been driving all sorts of cars for the last 20+ years and I've never seen anything like the 30% mileage drop I'm getting since it got cold out. I'm driving a '93 SC2 and since it got cold (by cold I mean below 40 degrees F) my mileage had dropped like a rock. I'm finding it really hard to blame it on winter blend fuel and warm-ups(which I rarely do anyway), unless this is normal to Saturns. By the way, I just changed my ECTS and it didn't help, probably since the one I removed was brass tipped and in good condition. Any other ideas?

Thanks

Originally Posted by wolfman

With winter blend fuel, COLD weather and remote start warm ups, my 97' SL2 automatic is down to 24~26 mpg 75% city....and there is not a thing "wrong" with it I assure you. When summertime rolls back around, I'll see 32 again I'm sure.

[96GSL1]

30% is not normal. Our gas milage dropped 6%.

[DarrylLeeOHS30]

I dont really have anything to compare to the winter fuel since I didn't get my gas mileage problem fixed until the winter-blend started to come out. from about july of this year to right before Christmas i had been getting ~20 MPG, due to a bad thermostat, ECTS, dirty EGR, TB, bad Wires and a slew of other things. With fixing all that in the middle of winter (with LONG warm ups and mostly city driving) my mileage is at 33.33 MPG as of the last tank. I can't wait to see what summer holds!

[hsv sc2]

I'm slightly south of you (al) and only see a slight drop in mileage in the winter, though I usually blame the long line into the base for the drop. Usually get around 30/32 mpg in town. Too busy to get any higway mileage in :<.

[angelnut]

Been a while since I have been able to visit the forum...

We moved from South Denver to South Greeley (Evans) during Thanksgiving weekend. So now I drive farther to work than I did before. Only this time it is almost all country roads (55mph+) and highway driving. Oh and my car doesn't sit out in the driveway all night anymore...we have a garage again. Not sure how much of a difference that makes, but it doesn't take as long to warm up.
I noticed that I wasn't getting the same gas mileage as I was last summer (40-42mpg). Since it has gotten colder during the days, my mileage went down to 35 mpg so I ran a bottle of injector cleaner through it and it seemed to run smoother, but no improvement in mileage. So hubby ran another bottle through it AND I ran a tank of Premium through it at the same time. My mileage went up to 37 mpg.
The only thing that I noticed that is different from summer is that now that I am not sitting in traffic, my temp gauge doesn't get past the first mark very often. And if I turn the heat up past half, its closer to the C mark most of the time. I have been debating on whether or not to put some cardboard over one side of the radiator or not. That might help my mileage go back if its running warmer (about halfway-like summer).
I also rarely run the regular in my 94 sc2, I run Premium all summer and go back and forth between Midgrade and Premium all winter, depending on the daytime temps. It seems to run smoother even during the winter. Although it sure hasn't seemed much like winter here on the front range...the mountain has been getting almost all the snow and cold so far.

Oh and by the way, I went from driving 70 miles a day to 98 a day with my SC2...from Evans to Boulder 5-6 days a week.

Lori
Evans, Colorado
94 SC2
197,??? miles

[j_w_younsgter]

92 SL2...supposedly getting lousy mileage and the temp light on the dash is coming on...(my son is driving this car)....any clues?..the temp sensor driving the computer?...supposedly the water pump was changed recently....how can you check the water pump is actually working without tearing it out of the car?...

any ideas would be appreciated....I'll poke around the car this weekend.

[rugevit]

Originally Posted by j_w_younsgter

92 SL2...supposedly getting lousy mileage and the temp light on the dash is coming on...(my son is driving this car)....any clues?..the temp sensor driving the computer?...supposedly the water pump was changed recently....how can you check the water pump is actually working without tearing it out of the car?...

any ideas would be appreciated....I'll poke around the car this weekend.

Welcome to the board...

The most things ive seen that it might be on that would have to point to the ECTS (Engine Coolant Temp Sensor) which might account for some of it. As for the temp thing...could be a sticky sensor in the coolant tank or could even be that the coolant is off the correct percentage some. Ive heard that they can be quite sensitive to it. There might be a couple other things i might be forgetting, but someone out there will usually have the answer