I noticed that my 08 Entourage has a compression ratio of 10.5:1 and burns regular unleaded. That's fantastic! My question is, has anyone used premium fuel with a higher octane and got different results (better fuel economy or power)? I am wondering if the computer uses the knock sensor to keep the timing in check, and if premium is used, would the computer alter the parameters and adapt for the higher octane fuel to give even better power or economy?

Your assumptions are generally correct. The answer is: it depends. If you drive it lighted loaded in mild weather with a feather-weight rightfoot, you won't see much difference. OTOH, if you load it up full of people and summer vacation gear, tow a trailer going up steep grade in 98 deg F and 100% humidity, your Entourage will sure appreciate being fed premium.

The difference in fuel economy won't be dramatic in any case. I do put higher octane in our '06 Sedona in the hottest months here on the Gulf Coast. Up there in Canada, I suspect regular unleaded will do just fine year round.

Take a look here for a bit more explanation: http://www.hyundai-forums.com/index.php?s=...st&p=244444