why would my '99 buick regal suddenly get approximately 100 miles less a tank?

Asked by Dec 01, 2016 at 08:21 PM about the 1999 Buick Regal GS Sedan FWD

Question type: Maintenance & Repair

same route every day, regular maintenance, I used to get about 350miles to
the tank and now suddenly I get about 220 miles to the tank. What is wrong
and how do I fix it?

2 Answers


Check the engines tuneup condition, air filter, plugs,etc. Has the stations switched to winter fuel grade? If so a lot of cars loose mpg with the stuff. You could try an octane booster, something like 104 or similar, see if that brings the mileage back up. The more expensive route is to have the system"live data" scanned, the tech would be looking for some sensors for incorrect readings being feed into and the computers response to those readings and then compaired to what the actual readings should be, and then tell what is going on.


I have had the knock sensor go haywire and it was sending a way high signal to the ECM causing the ECM to retart the timing all the time...this affected performance and gas mileage

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