what fuel is required?

If you don't have the owners manual..Google it, you will find it by keywords 2006 Pontiac grand Prix GXP

OK sorry for being cynical. I did it for you Regular, 87+

Side note. I have a friend that owns a gas station. There is no such thing as mid-grade fuel from the refinery, they simply put X gallons of regular in the storage tank, then add premium, 25% of X gallons and weights and measures do not regulate that..all they care about is you get Y gallons when the pump says Y gallons and you pay the posted price, i.e. accurate calculation of gallons pumped and what you pay ..somebody should actually check octane but that's a different story., it's not weights and measures

i HAVE a GXP in 2006 attitude. When I first got it, which was December of 2012 with 199,000 kilometers the engine ICON was out. I put regular in it the ICON went on. The next fill I put Premium in it. The ICON went out. It stayed out till I put regular back in. I have switched back to Premium from MOHAWK HUSKY...ICON did not go out...I tried the cheap COSTCO premium...the ICON did not got out...I tried the stuff that works my WifeePoo's Passat 2.0 turbo...Shell premium at $1.37 a litre...didn't work...ICON is still on...time to read the codes...gulp

I know this is 4 years old but thought I should put the correct answer. It takes premium gas http://www.fueleconomy.gov/feg/bymodel/2006_Pontiac_Grand_Prix.shtml