#1: Mpg drop Author: bmw325i, Posted: Thu Jun 08, 2017 6:11 pm ---- It's been a long time since I posted but work, family and plus the car has not been a major pain till NOw, lol.
My 97 540i auto with 248k now on the odometer has been dropping mpg like crazy. I used to get 21-22 mpg mixed driving. Now it's down to 8 mpg.
I can't smell or see any fuel leaks. The only code I am getting on my basic reader is P0430, I am thinking my cat is going out since it's rattling, but even with a bad cat can that be the cause of the mpg drop, more than half?
I don't have in depth code reader and can't tell if there is something more to it for the bad mpg. I scoured other forums but could not find anything related to my issue.
Another thing I am noticing is my speedo and mpg gauge are all over the place when I drive as well.