https://www.mobil.com/lubricants/-/m...pecs-guide.pdf
Notice on every Mobile 1 oil with API certification the recommendation states "Vehicles that require XW‐
XX."
There is not one spot in their product guide that recommends using a viscosity not originally recommended by the manufacturer.
Notice the zinc and phosphorus content on the racing oils...
Again, this whole topic is grayed significantly by the regulations governing oil, fuel economy, emissions equipment, etc. Aviation oil still has or recommends as an additive, Tris(methylphenyl)phosphate (Tritricresyl phosphate). Long banned in automotive oils and with relatively high toxicity, but in a market that is widely unregulated. A market that suffered many of the same issues listed in Hib's articles, such as the ceasing of lifter production by Eaton who's secret sauce recipe for lifters supplied aviation for a long time.
Another good read for those who really want to get into the weeds:
https://www.mdpi.com/2075-4442/1/4/132/htm