Shell became a well-respected name in aviation during WW2 when they produced tons of 91 octane aviation-grade fuels (which, for conformity, actually ended up in virtually everything that used gasoline).
What REALLY promoted their brand tho’ was their development/production of TCP (tri-cresyl-phosphate) which saved high-compression, supercharged and turbo-compound engines from detonation by allowing super-high octane leaded fuels….but which created additional problems due to lead fouling….which the TCP solved.
Phosphates were also introduced by Shell as a wear-preventative in lubricating oils…. and the Rest is History…. making Shell one of the early Big Names in aviation circles.
Other mfr’rs caught-up and are equally good now that Shell’s proprietary, exclusivity has expired.
Phillips and Mobil also enjoy good reps… Exxon tried an aviation oil for piston engines but that didn’t pan-out for them, but their 2380 synthetic turbine oils are well-respected….and, of course, now Exxon (descendant of Standard Oil of Ohio…ESSO… and Mobil (descendant of Standard Oil of New York, ..SOCONY….are re-united as one company, having been split up back during the anti-trust/anti-monopoly days (Sherman Anti-Trust).
Ain’t it funny how things seem to repeat themselves.