Originally Posted by KrashDH

And to Jeremy...I have had my aftermarket for over a year now, and I haven't thrown any codes. I did notice you said poor aftermarket cat. The Magnaflow seemed to be reputable that's why I went that direction

Originally Posted by KrashDH

Did your MPG's go back up after the OEM? I had around 18 mpg when my OEM cat went bad. Usually cat's don't go bad unless the sensors are gone, because that is what regulates what is being burnt up inside of them. The harder they work, the less time they will last. OEM though IS the best replacement because of the metals used in manufacturing. My mpg dropped about 1 mpg when my cat went bad. I could tell this was the case because the honeycomb that is inside was coming out of the tailpipe and the rings that are tack welded inside were rattling around.

You could say that having an aftermarket cat would be similar to straight piping your vehicle (since they aren't as efficient). Even when you straight pipe your vehicle you won't lose that many mpg's.

I live in MT so I replaced my cat with a Magnaflow aftermarket cat. Have had NO issues with my mpg at all. With that replaced and my O2's replaced, my gas mileage has gone back up. It seems fishy to me that you would drop up to 8 mpg just because you had an aftermarket cat... they might not pass emissions in CA, but they seem to be legal (and work for that matter) in other states...

And to Jeremy...I have had my aftermarket for over a year now, and I haven't thrown any codes. I did notice you said poor aftermarket cat. The Magnaflow seemed to be reputable that's why I went that direction

Originally Posted by jeremy9allen

Some people just don't think there is a problem when your check engine light FLASHES at you.