so first tank of gas since it started to get a little colder out 60-70degrees vs 80's. car went from 26mpg to 17mpg..

 

i need to check the codes cause it does flip the check engine light once in awhile.. otherwise runs fine.. it has no cats and is straight pipe to the stock muffler. and it does have an 02 sensor. nothings changed but outside temps really..

 

91' legacy 5-speed 101k

I just had the same thing happen. I fixed some oil leaks by replacing the valve cover gaskets and missing spark plug access seals, new plugs and wires.

 

Went from 23mpg to 26mpg, then the last three fills have dropped down to 19mpg.

Mileage will take a hit if they upped the ethanol content, or started adding ethanol.

 

Winter blend, eccch.

 

Dave

Has anyone else had this high of a loss just due to fuel problems though? I'm still buying fuel at the same place as before my mileage got so much worse.

so i finally got around to pulling codes

22 = knock sensor

32 = oxygen sensor inop

35 = evap

 

the o2 sensor code is prolly from when i ran without it for a week when i did my custom y-pipe.

 

i wanna clear the codes and run it a week to make sure i am getting the right ones for my issues but i tried to clear the codes and they would not clear. didn't matter what i did..

 

any tips on clearing them?

disconnect the battery over night.

Your MPG will tank way down when you have an O2 code. Fix the problems, clear the codes.

Those codes are your answer.