> I've tried to find a table that relates the engine compression to the
> recommended octane of gas to use,
No such thing, it depends on way too many other variables, including
combustion chamber design, intake and exhaust manifolds, even cam timing.
> So far, I've always used premium. However, if the car doesn't need it
> that's just wasted money.
> What is the wisdom of the list?
If it doesn't ping under any conditions, it's high enough octane. Try a
lower grade for a tank, or two and see if you can make it ping. If so,
you're not wasting your money on better gas.
The owner's manual says to use 95 octane (Research method) ... but at least
here in the USA, pump gas is rated by the (R+M)/2 method (average of the
research and motor numbers) so it's not clear just what 'pump' octane meets
the book requirement.
Gas quality varies anyway, I just bought a tank of "88" octane that pings a
bit. Won't be going back to that station soon.
59 TR3A TS39781LO daily driver (back on the road, woo hoo!)
71 Stag LE1473L daily driver wanna be (waiting for J-type transplant)
63 Sports 6 HB7826LCV rustoration project
57 TR3 TS21731L rusting quietly