What's going on with my mileage? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 09-27-2006, 11:04 AM   #1
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Default What'* going on with my mileage?

I'm very puzzled.

My mileage has dropped 2-3 MPG even though my driving habits haven't changed.

It was time for plugs and wires, so I went with Beldens and NGKs. I checked engine vacuum, normal, and did a compression test, all cylinders right around 155. Oxygen sensor about 10K ago (Delco) which resulted in no change in mileage.

Any ideas, guys, besides a midnight stakeout of the vehicle with my 12-gauge?
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Old 09-27-2006, 11:13 AM   #2
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Do your fuel blends get changed around this time of year like they do in my area?

Changes in the fuel blend can seriously effect MPG.

Take for example a trip I took to NY a year ago. Way there..mileage was great. Way back...mileage sucked and I drove slower and better..mileage wise.

NY Gas is known to contain mileage and power robbing ingredients .lol
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Old 09-27-2006, 11:34 AM   #3
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California has oxygenated gas (10% alcohol) year-round, but the car has always gotten 20 MPG with little difference between highway and city driving since it was new.

Guess that makes sense, though, I'll check it out.
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Old 09-27-2006, 11:41 AM   #4
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Air filter, tire pressure, lack of wax can be factors.
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Old 09-27-2006, 12:19 PM   #5
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Lack of wax?
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Old 09-27-2006, 12:23 PM   #6
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Quote:
Originally Posted by Mike1995
lack of wax can be factors.

I can't wait to hear this one!
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Old 09-27-2006, 12:31 PM   #7
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Less resistance don't ya guys realize...

That'* slowing you down ever so little.
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Old 09-27-2006, 12:34 PM   #8
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Right. Which explains why military aircraft are commonly painted non-gloss, and why nobody that runs at the salt flats waxes for speed?

Ok, we had our fun. Back on topic. :lol;
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Old 09-27-2006, 05:19 PM   #9
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Its probably like Boosty said the gas formula changes I think Sept 1 to the winter brew.
Have you run fuel injector cleaner lately?
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Old 09-29-2006, 11:13 AM   #10
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wow that would make since! My plugs and wires were totaly bad so I thought that was my MPG problem. I changed them and it went from 20 up to 22 mpg but that is 3 mpg lower then I got all summer. and yes I just started noticing the problem with the colder weather in september and the damp dew in the morning is how I found out my plugs wires were bad.
wInter blend gas has MPG robbing chemicals in it?
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