Well, this Summer looks like its gonna be a blazer.

What sort of engine oil would be good to use here?

I ask this cos we have different brands and types being sold now.

Above 86 fahrenheit the Gregory manual says a straight 30 weight oil like Morris's.

Otherwise between 32-86 degrees F you use a 20W50.

Personally I like the all round abilities of a 20W50 for the old clunker. Oh, but find one with high zinc levels or add additional zinc so your tappets don't get eaten away.