Prior to 2017 either the Quaker State oil grade used at Wal-mart Auto Centers in their basic oil change or Shell Rotella had enough trace element zinc (on a Parts Per Million or PPM basis) to be good for older car engines other than high performance products of the 1960's and later. This would have included K-F and Willys or Jeep vehicles. During 2017 these two oil brands were re-formulated to "improve" them and bring them up to the current SN standard of the American Petroleum Institute (or API) and zinc along with a few other trace elements needed in older engines were dropped as part of the re-formulation proicess. This is from the customer service departments of both oil brands (which are owned by Shell aka Royal Dutch Shell Oil).
This is important for the metalurgy used in older engine blocks and component parts required lubrication with a motor oil having at least 1100 ppm of zinc and other trace elements is needed for proper protection of crankshaft, camshafts and bearings (both types) for engines prior to 1965.
The classic car sold by Hemmings as well as the VR1 grade of Valvoline oil are two times of oil with at least 1400 PPM of zinc according to the customer service departments of these brands. At present, I am using 30 weight VR1 in our Henry J Corsair deLuxe; 10W-30 will also work where it gets colder than the Seattle WA area (normally we don't get below 30 degrees F. during the winter). At last check (about 2 weeks or so ago ) O'Reilly stores were offering the 30 weight on sale at 5.99/quart plus tax with free shipping to one of their stores if they did not have the desired grade in stock-regular price is $7.99/quart plus tax. Normal "case lot is 6 quarts, and for our HJ a case covers the 5 quarts needed for oil change (per factory shop manual for a 6 cylinder, 4 qts for 4 cylinder: figures are for cars without oil filter) plus an extra quart if needed.
