Fuel

The engine has a knock sensor system, so you might be OK. Read the owner's manual and decipher whether it says "Premium fuel recommended" or "Premium fuel required". Also, in the specifications section there may be a blurb like "Minimum fuel octane required......"

Generally, if the car is set up for premium, that means a posted pump octane of 92 or more.

I ran 87 in my '97 Deville for at least 3 year once I learned about the knock sensor. I never even noticed any difference in performance or mileage. As Sub said it has a knock sensor and if it detects a spark knock, it will retard the timing appropriately. That is all that will happen. Oh yeah, you'll spend less money on gas.