1999 Bonneville Sle gettin horrible gas milage - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 01-17-2004, 11:17 PM   #1
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Default 1999 Bonneville Sle gettin horrible gas milage

I am in a pickle and can not figure out why I am losing so much gas milage. I am currently at 99k miles. I recently change plugs, wires,air filter,o2 in the manifold, new tires with right pressure and alignment. Getting 325 to a tank around 18 miles per gallon. I drive 1 mile to the freeway then 27 freeway miles and 1 more mile to work each day. I am stressing here that 27 of my miles are freeway and I do not sit in any traffic. Tomorrow I am changing the o2 sensor after the convertor but believe that will not fix the problem. Check engine light is not on, and not burnt out either. I hat paying 100 bucks to have it checked at the dealer so help me with some suggestions as to what I may be missing her.
Thanks,
Rich
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Old 01-17-2004, 11:30 PM   #2
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Yeah, that 18 mpg figure sounds kind of low. You should probably be getting closer to 24-25 mpg. How do you calculate your fuel usage?
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Old 01-17-2004, 11:42 PM   #3
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I run the tank bone dry.....put 18 gallons in and then divide by the number of miles I have driven the next time its bone dry. And thats been between 335 and 325 the last three tank fulls. I was used to getting 430 to 440 a tank full until this past October til now.
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Old 01-17-2004, 11:51 PM   #4
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Runs fine other then the MPG tho? If so... maybe a throttle body cleansing will do the trick. Or maybe your tires are just a little low on air.
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