1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

gas mileage

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Old Mar 20, 2005 | 01:17 PM
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Default gas mileage

what do you guys usually get in town i get about 200 miles to a tank at the most usually 170-180 and that just seems way to low....i have tryed drivin like a grandma but it doest help. before i changed the plug wires i would get about 215 and i had one wire that was bad so i thought fixing it would accually help.
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Old Mar 20, 2005 | 01:59 PM
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Cold weather lowers mileage. Also, don't use Bosh equipment. If you put in Bosch plugs and wires that may be why it lowered more. Replace you're oxygen sensor that may also help. BTW- this type of post should go in the 92-99 troubleshooting section.
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Old Mar 20, 2005 | 02:26 PM
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I still get at least 25mpg in the winter in my SSEi (29-30 hwy in the summer). You have issues. And I agree with staying away from Bosch. O2 sensor is usually the culprit after 50k or so.
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Old Mar 20, 2005 | 09:05 PM
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yes. 180 miles is horrible for an entire tank. I usually go 170 miles for per 1/4 of a tank! (tank is 18.5 gallons)
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Old Mar 21, 2005 | 12:13 AM
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my 93 is getting ~20mpg with driving being about 50/50 city hw I have a 16gal tank
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Old Mar 21, 2005 | 01:29 AM
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yeah your car is the same year as mine and 20lbs heavier so uh you should be a little better off than that.

The worst I have gotten in strictly city was 260miles to the tank (about 16mpg or so) and best strictly city is 20ish it seems which is 300 miles or so to the tank.

highway you should have 350 on the trip meter and still be far from hitting empty.

again make sure you throw in (if you have not already):

GM O2 sensor (like 37 bucks from gmpd)
make sure you get a PCV valve too from gmpd if you get the O2

new DELCO plugs gapped correctly (rice HQ usually has em)
new wireset (most will work)

after you do that and still get crappy miliage it is time to talk about it.
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Old Mar 21, 2005 | 02:08 PM
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Default MPG

I noticed the guys getting exceptional mileage on the previous MPG sticky all had High flow cats.
Could this be the cause of my low numbers on my 99?
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Old Mar 21, 2005 | 06:01 PM
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I am currently dealing with a gas mileage issue on my 93 SE and I'm getting a bunch of parts in soon so I can get to it on Saturday. I'll be doing an O2 sensor replacement, fuel filter replacement, air filter and serpentine belt replacement. My mileage has also tanked. My plugs are new, but the wires are not, but they test OK. I might try replacing the PCV valve like what was mentioned earlier just for the peace of mind.
I'll let you know how my experiment goes.
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Old Mar 22, 2005 | 12:32 AM
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I get really strange results, sometimes good tanks (18 mpg in the city), sometimes bad tanks (18 mpg on the HWY). I am replacing the o2 sensor soon, this should help things out i hope.
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