I remember when I first checked into the
Amsoil products, they were making claims about reduced operating temperature. This included manual gearboxes and rearends. They touted that the gear lube allowed bare handed rearend gear changes when a race car was up to full operational temperature due to the reduced friction.
I never noted engine temperature reduction on the cars I've used the product in. It did tend to find it's way out of the engine & tranny more readily than conventional petroleum based products. These vehicles usually had a lot of miles on them as opposed to the change over just after break-in. Still, all in all, no complaints. I use Castrol Syntek in our MR2 turbo. (I saw a number of web sites that recommended it.) The Cobra is not broken in yet, so it's still using non-synths.