I've been using Toolstation SAE 30 oil in my old (1980's) mower. I was thinking this could be a good get-you- home top up as filling stations are few and far between now and Toolstation branches seem to be everywhere. Just a thought.
Good idea! If you can't find a Toolstation then Screwfix also sell SAE 30 oil. Better than spending an arm and a leg on a litre of entirely the wrong oil in a petrol station!
It is API SF so likely fine ft or an older engine with roller bearings and not too stressed.
I've been using Castrol GP50 on the ZB/BB this 'Summer'but on recent cold days it's been hard work to spin over!
Thankfully first or second swing starter from cold.
Winter I've been using Chatsworth 30 for years.
It surprised me -the difference.
Also got EP90 (GL4) in gearbox.