I just sold my GMC 8.1 gasser, and brought a new 2500HD,4WD LTZ crew cab,with 6.6L DURAMAX DIESEL,Allison, 3.73 ratio.With 365 hp and 660fpt it's a great TV.The Diesel Particulate Filter,cleans it self while driving it takes about 20 min.These are B5 BIODIESEL COMPATABLE they can run on 95 percent diesel and 5 percent biodiesel.