Hello so i have a 99 buick regal GS and for some odd reason iam getting horrible gas mileage just this week ive had to fill up 3 times. Icommute to school everyday which is 50 miles round trip at 70-75 mph. If iwas to fill up on a monday id have to fill up again wednesday or thursday . Ihave no trouble codes at all . Can somebody please give me an idea of what can be goin on? I have done a voltage test on my MAF sensor ican test again if need be . Iam going to replace the sparkplugs and fuel filter tomarow .