amsoil synthetic,and their oil filter system is the best you can get.I ran a 1993 freightliner 100000 between actual oil changes.Cat had me do oil sample every month.Oil was always good,cat use to say every sample was bewtter than the previous one.I run GTX synthetic in my cars,as they only get driven short miles.Synthetic oil doesnt break down like regular oil.Oh And I ran a straight weight oil.If you want,multi weights are ok.5w40 will cover both very hot and very cold days,but the synthetic will make for easy starts in the winter time,thats why the 5w,its actually thinner.For those that swear by Lucus,the bottle says 20 %,thats 2 bottles per oil change,not one like everybody does.I quit useing Lucus,my oil samples got better,your just waisting your money.My truck at home has 980000 miles,with a cracked head,but the lower end doesnt have a problem,have used Rotella most of its life,if it werent for the cracked head,would of had no problem get over million mile on the Motor,and oil was change every 20000 miles.
Use gtx synthetic in my car did help the gas mileage,and in my Trans am it actually cut a tenth of a second off the quarter mile times.I believe in synthetic,my new truck will getting amsoil as soon as the motor gets broke in,if you put it in too soon,the rings wont seat
