City Mileage Drop Cause?

My 1990 Grand Prix is experiencing a slow drop in its city mileage although highway MPG seems steady. The engine has a lot of miles so I'm sure its due
for a rebuild. What typically causes this?
Jack.
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although
due
what's your gas mileage and how did you calculate it? weather conditions and quality of fuel is also a factor. did you ride with or without passengers during the times you calculated it? do you have an on board mileage computer?
many things to consider.
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What is the mileage? How old are the plug wires, distr. cap, rotor, spark plugs, etc.? When was the last time you had the transmission serviced? Do you check your tire pressure regularly? These are just some of the things that can affect gas mileage. I believe that you can get updaed Proms for worn (read high mileage) engines and that may help. Sometimes it's the little things, even driving habits, that can affect gas mileage the most.
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Hmmmmm an engine with a lot of miles? I'm getting 18- 20 in the city 26-28 Hwy and I got a hell of alot of miles and don't need a rebuild.
========Harryface ======== 1991 Pontiac Bonneville LE ~_~_~267,300 miles_~_~_
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This might be a shot in the dark, but I have heard that "winter" formulated gas in the cold weather states can cause a drop in MPG. And it is that time of year.

although
due
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