My apologies for the earlier post regarding Royal Purple Max Gear. That was based upon outdated information on the Pep Boys website. That same information indicated that RP Max Gear was yellow metal friendly, and yet it would appear that it is among the worst offenders in that regard according to ASTM D130 test results posted here and elsewhere.
This evening I topped off the vintage 1985 Troy-Bilt Pony with Mobil1 75w140. Hopefully it will not prove too thin for that application, as it appears that yellow metal friendly 85w140 gear oils are stored next to the unicorns, leprechauns, and honest politicians in every auto parts store.