The year/model/engine would help. The 4 cylinder engines are designed to run on regular. The Gen II (2004 on) 6 cylinder is designed to run on premium but the computer will retard timing (you'll lose some poewr and fuel mileage) to allow use of regular. I suspect the Gen I 6 cylinder is the same. The information should be in your owners manual and on a sticker (if premium is recommended) inside the gas filler door.
Cheers
if its regular gas
Regular.
Yes
Never put gas in a diesel car. And never put diesel in a gas car. An engine is built to handle one and not the other.
Regular unleaded.
Regular unleaded
Regular Unleaded.
" regular " unleaded , 87 octane
You will risk doing damage to the catalytic converter(s).
regular gas or if you wanted to you coul put high test in it, its your choice.
In order to preserve the motor in your CTS you should put only premium gas in it.
No, you can't.