When I was at Ford Motor Company Engine Plant #2, I made the acquaintance of an engineer who's speciality was in engine lubrication. He said that the current grades of motor oil lacked trace elements of zinc and certain other minerals that older car engines needed. In the case of Henry J engines, for example, the zinc was critical to proper lubrication of the camslhafts and camshaft bearings because of their metalurgy. At present the current grades of regular motor oil (SJ, SL, SM, SN and the coming SP and SQ formulations) do NOT include the trace elements. Turns out that the special "racing" oils have these missing minerals. Valvoline VR1 and Hemmings Motor Oil are among the oils with the required (or higher which is good) levels of the minerals. I have used Hemmings, but local commercial old car restorer and K-F club member Randy Sargent recommends the Valvoline VR1 as it's levels are a bit higher than the Hemmings offered product. According to Valvoline, they do not make a 20 weight straight but do make a 10W30 and a 30 weight straight oil. K-F recommends 20W oil for HJ engines in summer and 30W for the 226 in summer. Hemmings do not make a straight weight that I know of, so I go as close as possible with the multi-grade product. Since I rarely drive my HJ during the "off season" (temperature and wether conditions generally allow for year-round driving as a rule here in Tacoma WA) I will use the 30 weight product. No complaints from the car so far but I druve less than 2,000 miles/year.