there have been a lot of post on whether to use non detergent or detergent oil, the easiest way to answer that question is to take the time and take apart an engine that has been run on non dertergent oil and look at the god awful amount of sludge built up in the pan and valve chamber, then you deceid if you want to follow the manual thats over 80 yrs old on what kind of oil to use, then you make the choice