For all the British vehicle experts/nuts

[Grant Bowker]

Sorry, I had meant to put this link to Shell's aero piston engine oils in my last post https://www.shell.com/business-custo...oil/about.html
It looks to me as if their numbers are twice the SAE viscosity (e.g. AeroShell 100 is a SAE 50 oil).
In terms of RPM, compared to most modern gasoline engines the Merlin is low revving, limited to 3000 RPM (also compared to diesels in North American pickups, my Ford is limited to 4000 although I haven't taken it near that - no need and I don't want to listen to it at that speed). As a 27 litre engine 3000 should be enough for the Merlin....