I appologize for the mix up here. I got the years floped on my grand prixs. You are absolutley right that all 06+ GT's were supercharged. Kinda embarassing to not know the years of my own cars and be called out on it. Oh well. 2005 pontiac grand prix gt( not just badged) (have docs.) and 2006 grand prix gxp. Mileage is correct for both models listed above. Just years swaped.