I've run all the Supertech oils in my beater/daily driver jaguar w/ the AJ 6 engine with no adverse effects and it now shows 213K on the clock.
I ran the 15/40 last fall for a 3K interval and had no issues with it. The AJ6 however, is easy on oil - huge 2+ gallon sump, big oil cooler, big filter, and the engine does not strain much, so I could probably run corn oil for 3K without damaging it .... I would use the supertech 15/40 in it this Spring, except I am going to play with the Mystik 15/50.
The only supertech I've had any issue with is the 5/30, which at 2.8K has now seemed to thin a bit, consistent with an analysis that was posted, but maybe I was ambitious putting this in an engine with so many miles on it.
Despite the apparent good luck I've had in my beater, I DON'T run Supertech in my wife's jag, my other jag, or our other cars and trucks - I prefer to spend a bit more on them ...