Ok had my car about a week now, only filled up once, but without the owners manual that the dealer "promised" to find me, i wasn't aware that inside fuel door said premium unleaded only (found out tonight when opened door). How Important is it really to use premium unleaded?
would plus work just as well ?
I understand using it for the performance and the injectors.

 

they all work , I use 89 octane and every third tank full I use 93 . 87 will even work , just don't get used to it . Also stay w/ one or two gas stations so the gas quality doesn't vary . And stay away from the no-name gas stations , or else you'll be pinging by the end of the week .

 

It's crucial that you use the octane the car was designed to use. Since the CL-S and TL-S engines have high compression ratios, they require premium 91+ octane gas to prevent from detenation or pinging.

CL/TL have mechanisiums to prevent when you use 87 or 89 octane, but it's not advised to use lower octane. You may experience more miles per gallon, but you will also notice that your car will not response how it's suppose to.

In the long run it will most likely cost you more to use 87 or 89 octane than it's work saving the extra 10-20 cents/gal.

 

Wont really matter if u put in lower octane couple of times, but its best to use 92+ for best engine performance.

We paid thousands for a car so why not an extra 5 bucks for premium gas at the pump.

 

In this car it's important, because of the high compression ratio. Think about it? A high performance car that has 260HP? That just screams premium. You can use 87, or 89 sometimes, but it's not good for this engine for any long periods of time. However the car will still run ok, but you will get a decrease in performance. The computer will cut timing to prevent pinging.