I have a 2001 oldsmobile aurora 78,000 miles on original motor. the car misfires , backfires underhood,and excessive gas consumption,also sounds terrible at the rear exhuast. Has anyone had these problems if so i would appreciate some help. thanks. 3.5l motor issue stated after i filled up at
cheap gas station.

Perhaps you answered your own question.
Filled up at cheap gas ...

Maybe you got some water in the fuel..

Siphon out a galllon or so,, let it sit and see if the water seperates from the gas..
Try some dry gas.. or siphon off half a tank and fill w/high test ..
burn it all off and fill again with known high grade gas.

Perhaps you answered your own question.
Filled up at cheap gas ...

Maybe you got some water in the fuel..

Siphon out a galllon or so,, let it sit and see if the water seperates from the gas..
Try some dry gas.. or siphon off half a tank and fill w/high test ..
burn it all off and fill again with known high grade gas.

I will give it a try and see what happens, thanks