The above comments reinforce the need for basic introductory guide to Seven owners, free of pet complicating notions (but mentioning steering arms!).

The book “Which Oil” seems to be about the only one of the type available now. I dont think the author is an oil development engineer or chemist, more a moderately clued enthusiast. His oil change recommendation are absurdly conservative, esp for warm Oz. He is obsessed with static viscosities and time stability of, but completely ignores the question of instant viscosity under high shear of non synthetic multigrades. (The possible case for 30 in racing engines, and probably the real reason for use in Porsches)

Has anyone clearly established that current oils in an old jet fed engine with cleaned sump lead to trouble? I have seen many laid up moderns from the 60s with heavy sump sludge and presumably elsewhere but no problems, despite many tiny oil holes in rockers, rapid oil flow etc. It seems a waste to chase about and pay a premium for an SA or SB oil of 1940s spec of the sort with which engines wore out in 30,000 miles, when API SG or better is available at the nearest supermarket.

As mentioned a problem with Sevens is that there is so much info available it needs a considerable degree of expertise to sort the wheat from the chaff so is only confusing to the present day newcomer.

The comment that thick oils sap power is very true. My car on straight 50 in cold Wellington southerlies could not attain top gear! 20W50 is a long way from 20 and notably thick at normal temps. The static viscosity charts in the book interesting (but when comparing watch for changing scales). The author overlooks that fact that noise and leakage often factors in choice of oil, not wear.

Pressure loadings in a stock Seven very modest cf moderns

Location: Auckland, NZ