Sears Spectrum 20w-20 detergent bought in the bulk tank they had in the Sears garage, because it was cheaper. Used it in 1965 Rambler Classic two door three speed w/overdrive. This was good oil, made several cross country trips, used no oil whatsoever, and the engine was so smooth and quiet at idle you could not tell it was on. Passengers said my engine was off. Then for my 65 Honda motorcycle which I bought new when it was a small one room motorcycle shop, now it is a huge Honda dealership, QS 30 detergent. My friend said use non detergent because detergent is no good for motorcycle engines, which even then was low grade oil, but I went by the manual.