The chart is one of many taken from: A Study of Automotive Gear Lubes - pdf. link



This study is published by Amsoil Inc., and, surprise, Amsoil Severe gear 75W-90 comes out on top.

I'll take this one with a large grain of salt, thank you.

Bob

AAR 4-speed 3.91, Tor-Red;
70 440 6 pack Roadrunner 4-speed 3.54, Plum Crazy;
68 Formula S conv 383 4-speed 3.23, Electric Blue;
69 Barracuda conv Slant 6 OD4 2.94, 71 B5 Blue;
78 Lil' Red Truck, Red;
70 Challenger S/E. 505 6 pack, Passon 5-speed, 3.55, B7 Blue