Originally Posted By: Panzerman
15w40 was designed to be used in mixed fleets. When we bought Mobil Delvac, it would have little pictures of motorcycles, cars, pick-ups, tractors, dump trucks and tractor trailers. I know we used to use it in everything in PA. Tri axles, caravans, pick-ups, atc,s whatever without any problems. I think everyone has become brainwashed by the 0w20 fad. Really, 15w40 wont hurt a thing. Back in the day, the Detroit diesels would run straight 40Wt and my Dad would run that in his Dodge pick-up all year long, even in harsh below 0 weather and never had a problem.
People are not brainwashed by 0w20..You use the thickest oil needed that gets the job done. In my application 0w20 fits the bill perfectly, better cold flow and better gas mileage. I bet I can run straight 50 and the car would still work fine but this is bitog..we try to get the most benefit from our oil. In most other applications I would always follow mfr recommendations. Not just run 50 weight because thats what you have always used.