Real crappy mpg
Thread Starter
Launching!
Joined: Jun 2005
Posts: 232
Likes: 0
From: New Jersey
Real crappy mpg I think i've been getting real crappy mileage with my car. I have a '00 ws6, to a full tank I get roughly 200 miles to it, from full to the check gauge light I usually have put on around 180 miles. I have about 73500 miles on it, I get a service engine soon light that comes on for a while then goes off, I scanned it and it was for an after cat o2 sensor, so that shouldn't effect my mpg. Could my front o2's be causing crap mileage just not throwing a code, but then again I dont know if thats too likely. I just did plugs and wires about 1000 miles ago, fuel filter at 70k, ran fuel injector cleaner thru it, I mean the mileage sucks, but since I don't really my car that much its not really killing my wallet but I wanna know why the mileage sucks. I believe the tank is 16.8 gallons? so if I get around 200 miles per tank then I'm getting 11.9 miles per gallon, which sucks. Any ideas? Thanks 
change you o2 sensor that is going bad. if it is throwing a o2 the it is going into limp mode and it is running real rich because the computer is dumping a lot of fuel. after you get it fixed get your code erased, because you will keep getting bad gas mileage until then. I get better gas mileage with my set up. so something is definately not right.
Thread Starter
Launching!
Joined: Jun 2005
Posts: 232
Likes: 0
From: New Jersey
Heres the odd thing, the SES light comes and goes, and when I hook it up the scanner, and I watch the o2 activity, I can clearly see that bank 2 sensor 2 is bad because its not switching like the other ones, but what I dont get is why the light comes on stays on for like a 100-200 miles, goes off comes on again later on? odd? anyway I thought rear o2's didnt effect mpg, only monitered cat efficency. Also I have a SLP MAF its not descreened tho, maybe thats causing crappy mpg?
Yea, I agree with Black01.. Might as well change out the post cat 02's and go from there. Since you are doing one, do the other.
I got a a code like that and it ran like ****.. Put the new corvette ones in and no problems or codes sense. Start there and see if that works..
I got a a code like that and it ran like ****.. Put the new corvette ones in and no problems or codes sense. Start there and see if that works..
TECH Enthusiast
Joined: Sep 2005
Posts: 522
Likes: 1
From: San Bernardino, CA
I seem to be having bad miledge too. I only get about 120 miles with half a tank, about 15mpg.
I do about 60-70% street, 30-40% highway. I shift around 1800-2500 rpms. Most of the time I cruise around 1200-1600.
p.s sorry for kinda using your thread.
I do about 60-70% street, 30-40% highway. I shift around 1800-2500 rpms. Most of the time I cruise around 1200-1600.
p.s sorry for kinda using your thread.
cumbias it is most likely because you have horrible gas in califorina compared to the rest of the contry. when I was stock I would see all most 425 on a full tank on the highway. I would change the fule filter and plugs, and air filter.
TECH Fanatic
iTrader: (3)
Joined: Mar 2003
Posts: 1,162
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From: Bensalem, Pa, now montreal, Quebec
im getting crap mileage also, these cars especially m6s dont like pure city driving, im barely and i mean barely getting 13mpg, i have no clue where gm got 18mpg city for this car, id be lucky to get 15mpg. Ive been fighting this problem ever since i moved to Canada, car used to get 16mpg consistently, up here im struggling to get 13, for a couple months in the summer i was getting around 17, then it dropped all the sudden, car is fully tuned up, new everything. Have zero clue, im afraid to mod the damn thing, gas is very pricey up here as it is, if the car cant do better than 13mpg in the city in pretty much stock config, i dont know....
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TECH Enthusiast
Joined: Sep 2005
Posts: 522
Likes: 1
From: San Bernardino, CA
Originally Posted by black01_WS6
cumbias it is most likely because you have horrible gas in califorina compared to the rest of the contry. when I was stock I would see all most 425 on a full tank on the highway. I would change the fule filter and plugs, and air filter.
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after cat yeah i also thought they really just kept the front ones in check and made sure they where working. my milage is getting worse as well and before i reeplace the o2s it would be nice to know which ones do what. i am not currently throwing any codes.
Staging Lane
Joined: Aug 2005
Posts: 55
Likes: 0
From: \
Some cars do use the rear O2 sensors to maintain fuel control, for example if you have too much oxygen or too little oxygen after the exhaust goes through the converter the post cat O2 sensor will tell the PCM to adjust fuel trim, MPG has A LOT to do with your driving style, when I don't drive like a jackass I get just below 19 mpg all around on an 02 WS6 m6 . Generally manual transmissions are more fuel effifcient.
Originally Posted by Cumbias
I seem to be having bad miledge too. I only get about 120 miles with half a tank, about 15mpg.
I do about 60-70% street, 30-40% highway. I shift around 1800-2500 rpms. Most of the time I cruise around 1200-1600.
p.s sorry for kinda using your thread.
I do about 60-70% street, 30-40% highway. I shift around 1800-2500 rpms. Most of the time I cruise around 1200-1600.
p.s sorry for kinda using your thread.
On The Tree
Joined: May 2005
Posts: 135
Likes: 0
From: Midland, Tx
Im lucky if I can get 150mi out of a tank of gas. 
I have no idea why my car eats gas like this, Ive yet to throw a code for o2's, just for a high idle. 
But hey you got to pay to play right?? (I just didnt wanna pay this much to play)
I have no idea why my car eats gas like this, Ive yet to throw a code for o2's, just for a high idle. But hey you got to pay to play right?? (I just didnt wanna pay this much to play)
Everyone bitches about the gas in cali. Most people say they get bad gas mileage there as well. Im just saying what I have read from other people living in cali. What is the highest octane you can get? That might have something to do with it.
well i get horrible gas milage up here at school with just purely city driving. i only drive like 3 miles at a time and that is it. since it has gotten cold i let the car run for a while before i drive it. i am getting like 12 and not really driving that hard. these things run rich when there are cold too and not warmed up. but now on the highway i get 26-30 (depends on how fast i drive). i can go like 120 miles on a 1/4 of a tank. so a lot of it is how you drive your car i suppose
TECH Enthusiast
Joined: Sep 2005
Posts: 522
Likes: 1
From: San Bernardino, CA
The highest I've seen 91, and I've looked all around town. I remember that back when I was about 7 (early 90's) my mom would get 92 octane. Now 92 is nowhere to be seen in this city. Why do they lower octane like this.
I have no idea, I know that you have very harsh pollution laws. When I was in Indiana we could get 94 octane, and 104 at certain places at the pump. I am in florida now and all I see is 93, which isn't bad.