[Mean Green]

Originally Posted by funksoulkitty

According to Chrysler.com both turbo engines have an 8.1:1 compression ratio.

The GT requires 91 octane because it was designed to run on premium gas. What this means is that the ignition map the PCM uses was created with more ignition advance under boost. This is because the higher the octane of fuel, the more advance you can run safely (ie, without detonation). When you run lower octane gas in a car that is using an ignition map for higher octane fuel, you are likely to have detonation while under boost. Detonation will destroy your engine over time. Even though your PCM will retard the ignition timing if the knock sensor detects detonation, you don't want to be running your engine that way. While in high boost situations for example (let's say you floor it), your PCM would not be able to pull out timing quickly enough, and detonation/damage would most likely occur.

Thank you. Very well said.