It's one of those never ending questions.

So many theories, so many grades, fully synthetics, semi synthetics etc. The debate will roll on and on for ever.

For what it's worth, Bob Rawle recommends with Forged pistons to go 10w60 Fully Synthetic. I have had this in my scoob and found it a little too thin on the noise front, with excessive piston noise. It isn't doing any harm and my pressures and temps are fine, but I am going to change for something like a 20w50 (as recommended by Simon JGM) and see how that goes.

I'm sure you'll get some good recommendations in this thread, in the end if something seems to get "more votes" than others, then you won't be far wrong I'm sure.

Good luck fella!