Combines Semi synthetic oil question

RD, I would expect that each brand of Semi-synthetic varies in formulation percents. I expect that is proprietary to each company and wouldn't expect they would let that out to customers. If you want the advantages of synthetic oils, I would suggest using the straight synthetic. Their performances vary, however, and I would suggest you use the pioneering brand for consumer auto use, AMSOIl.

Yes Amsoil is a very good oil. I us the 15w-40 and am up to 450 hour oil change in a 100 hour change engine. John

usafarmer, I would not extend oil change periods too much without adding their by-pass filtering system to remove particles in oil down to one micron. Do you have that on the unit you mentionIJ