I run Amsoil in everything. I have had excellent results with the products since 1989. And when I say everything I mean Boat, cars, lawnmowers, chainsaws and Cummins. I also service two yachts near here and the owners insist on Amsoil. The oil I run in my Cummins is the 15w 40 Marine diesel with the Donaldson filter which I will change every six months until I get my odometer fixed. Then It will get changed every 6000 miles. I also am running Amsoil product in the differentials and transfer case and when the automatic reqires service I will put it in that as well. I ain't crazy, but I know it works for me. Check it out at AMSOIL.COM

 

Here is my .02....I have used Rotella T non-synthetic forever with excellent results and Fleetguard 3894 filters......I change the oil every 10,000 km (6000 miles).