Which grade oil should I use for my motor?

[vince1]

Yes, I've used Valvoline before with confidence.

Mostly now I use Castrol because it comes on sale once in a while at our Canadian tire store. Conventional 10-30 one change a year in the 66 C10 250 and the 64 Rambler 232. Synthetic in the Volvo where I run it out to the full 12000 km (7200 mile) oil change interval. The VW TDI has a 15000 (9000 mile) interval and takes a special oil 507.00 spec. I can also get that in a Castrol. Mobil 1 works too.

Additives, nope.