Get a sample of your crankcase oil analyzed. Dont know where you are located, but check around various truck dealers to see who they use to do analysis. If this does not pan out, call Giles and Ransome (CAT Dealer) in Bensalem, Pa. They will do analysis of anything. You call them, give them your credit card number, and for (if I remember correctly) it's like 28 bucks, they will send you the kit which has: -long thin plastic line (but sturdy!) to snake into your dipstick tube about 4' long -a sample bottle -an overpack bottle -a pre-paid tyvek mailing envelope. All you do is fill out the paperwork they give you as detailed as you can (oil make, type, number of hours or miles, engine make/model/serial etc etc etc.) Get it good and hot, drop the plastic tube down in there with the other end down on the floor, draw a suction on it, let it flow into and fill the bottle, drop that bottle into the overpack bottle, send it off to G & R, and in 5-8 days you will be emailed a complete report with recommendations as to what to do. They might even call you if the situation warrants. I have used them before and they are good people to work with. Had to talk to the girl in the lab on the phone (she had questions for me, I had a sample of my 1958 Waukesha gas engine analyzed and it threw her for a loop at first...hahaha) she really knew her shit and knew engines.