This explains why merging onto highways is so jerky. I give it full throttle in 2nd, shift at around 5k rpm, smoothly depress clutch and roll back into the throttle at the same time, it sometimes works smoothly, sometimes feels like I am going to break something. It feels unpredictable. But now...
I used to ask the same questions for the dozen or so sports cars I've owned. The old timers haven't changed their answer in 30 years since I started. Just run 5w30 Amsoil. In 20 years the answer probably won't have changed either.
I don't know if it was mentioned in the thread previously, but I just bought a manual Supra in stratosphere blue from Lakeside Toyota in New Orleans. No ADM, 62k sticker price. They let me talk to the master mechanic who had the certification from Japan and I had a 30 minute long conversation...