I note that the most available oil here in the U.K. specifically stated for use in vintage vehicles is 20w/50. I have to admit I don’t really understand the numbering I think it’s viscosity at high and low temperature. Perhaps someone could educate me. Will this be ok for my 216 engine. I keep reading about needing to add zinc when using modern oils. I assume that a vintage oil has this but again not sure.

https://www.halfords.com/motoring/engine-oils-fluids/engine-oil/halfords-classic-oil-20w50-5l

Thanks

chris