Ya got to love these oil threads. In the late 70's the hot oil used in Porsches (air-cooled, flat tappet engines) was Shell Rotella, because of the Zn and P additives; spirited use required changing at 1500 miles, which I followed religiously. I've been using it in my classics, cars and bikes, since then. However, having pondered Alan Goldwater's articles in the NOCNC Norton Notice concerning oil temperatures in the late 90s (only synthetics, and in fact, only Redline survive 2000 miles with their film strength intact), I've stopped running Rotella in my Brit bikes, and switched to Redline. One reason that these oil threads keep reappearing on this forum is that the oil landscape keeps changing in response to changing EPA requirements. Rotella may well lose its ZDDP content to be compatible with emission controls, and it was never designed for the 141C head temperatures our Nortons achieve at a steady 75 mph on a 32C day (Goldwater's data). I see that Rotella is offering a new synthetic now, so I may have to eat my words; Rotella T6 may indeed hold its film strength at our temperatures, but its 5w40 spec seems a bit thin for our use in the summer. Since Redline devotes itself to the high-performance, hi-tempertature extremes of automotive lubrication, I've decided to simply stick with them; it's too exhausting to do otherwise.
