Fuel type & MPG

[Dead Eye]

Modern fuel injected engines with knock sensors can adjust ignition timing and fuelling maps to make use of a higher octane fuel and give more power, our old carburettor equipped engines can't. It's possible that the better detergents in the premium fuel may clean the upper cylinder, giving slightly better combustion... in which case any benefit would persist for many tankfuls of ordinary unleaded.

My car definitely sees the best of the improvements which is no doubt because it uses fuel injection but your point about the higher quality and detergent properties of the premium fuel is bang on. I'm fairly certain that most fuel system cleaning products are primarily based on highly refined jet fuel.

As for my earlier data; this was done over a bout 6k miles on the 600 (about 2-3 k on standard, the rest on V-Power). The car starts are over about 4k miles, 1.5k on standard