Can you just answer me this what came first the chicken or the egg, because I do not know. I do know delo 15/40 { 300,000 miles} pulling trailers now on 3rd transmission but never touched the motor still runs great in my 7.3 powerstroke. I also use it in my 351w 427 stroker even in my jeep 4.0 high output and have had no issues. in any of these vehicles.I have read all kinds of good and bad about it do what you want I am telling you what I am doing and yes I have done plenty of research on the 15/40 delo
and again I say dam good
oil high quality base stocks big budget testing with top engineers /scientist doing the testing. Go Blue Go Chevron!