The simple fact is that the 3.2L engine "requires" premium fuel to obtain maximum performance. It will not make as much HP at full throttle with less than 90 (R+M)/2 octane fuel.

Contrary to what some have said on this site, the NA Crossfire's 10:1 compression ratio is not a high compression engine by today's standards. Many other vehicles with comparable compression ratios run just fine on regular gasoline. My daily driver is a 2.2L 04 Olds Alero (no laughing please) and it has a 10:1 compression ratio. We also have an 01 V6 Ford Escape that is 10:1. The Ford Escape Hybrid has a 12.3:1 compression ratio and it still requires just regular unleaded! So, the answer is obviously more complicated than just compression ratio. Valve timing profiles, engine materials, configuration and operating temperatures greatly influence the combustion process as well.

Here's a good article on regular vs. premium from a few years back:

http://www.usatoday.com/money/autos/...emiumgas_x.htm