Just some more input here, My Tr-3 currently is not running so I have no experiance with it and 20/50 oil.
Having said that I have an older Motorhome, 65,000 miles {460 Cu.In. engine} I was using 10/40 in it, it went through oil like a drunkard does alcohol.
last oil change I went to castrol 20/50, although I have only put about 200 miles on it, sence the change. It seens to be a reformed oil consumer. Previously with the 10/40 and driving it the same route of 200 miles it would have consumed at least a quart. I did do some minor tightening of the valve covers and intake manifold {Yes the valve covers were leaking but I don`t think a quarts worth in the 200 miles.}
I`m SOLD on the 20/50, especialy for a summer or fair weather only vehicle.