Mobil 1 Synthetic

Not sure about the diesel oil , but the mobil is some good stuff. We use around 9 tankers a year of engine oil at work. Used to have chevron, switched to another brand because of carbon deposits, it got worse. Then we flushed an engine, did a major overhaul on it, and put in the mobil. Ever since, ---no carbon! Keep in mind this is a two stroke, natural gas fired, large frame low rpm engine. But, the moral of the story is, mobil makes some good crap. I'll try it out and post back in a few months. If you can imagine being in a 55 gallon drum head first up to your waist with head studs hitting you about a foot apart in the legs, all the while using a scraper/ screwdriver/ hammer, or whatever will wrok to beat carbon out of the ports on a cyl.....get the point? Once we saw it worked good, we switched out all our oil to the mobil stuff. It actually washed a lot of the carbon out by itself.(detergent type oil) We did have to wipe some out of crankcases where it had dropped out nad fell in the oil pan, but thats very easy compared to standing on your head in a hot cyl. bore. It costs more, but is cheaper in the long run. May not be the best for these , but I'll bet its good stuff.