Thread: Premium and PCM

Ok ive been running premium in my gt for a few months now. Well about a month or more it started shifting really rough here there. It steadily got worse. My gf got me an overkill pcm for my birthday a few weeks ago. The shifting started getting real worse. I took it to the dealership today, and they wanted to the put the stock one back on which they did but the also found that my cat converter was plugged. The car was great now, but when I got home I put the overkill back in and the car ran great, im assuming since the overkill changed the shift tables that the problem became more apparent. So the cat being plugged must of the been the problem
Im assuming that running premium all the time plugged the converter...
but since I got the overkill pcm now is it safe to keep running premium of should I go back to 87??

yea but cant rich fuels plug the cat ? like what happened to me

Is premium fuel a requirement of the Overkill PCM in a N/A car? If not why run premium?

Im assuming that running premium all the time plugged the converter...

No. It wasn't the premium that plugged it. It may have been a "weak" cat to begin with and it could have reached the end of it's service life.
Or you may have been buying poor quality fuel that just happened to be 93 octane. Back in the day I worked at a gas station across from Courtland Center (back then it was the Eastland Mall) and the only difference between our 87 & 93 octane was that the underground 93 octane tank had 800 gallons of ethanol added to it (with no pre-mixing)when they filled the tanks. With the low margin on fuel for the gas station owners you need a station you can trust.