Now, I may be talking through my hat (
and I'm sure someone will tell me so if I am
) BUT, IMO a car specifically not designed to run on premium (like one with an under 9-1 compression) should actually run better with a Plus 89 octane or Regular 87 octane fuel. Premium ignites slower than the other to prevent detonation right
so therefore you should get faster ignition with the other grades which theorically should give you more ? power. Ok, now looking for my old Nomex racing suit.
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1973 GTV - bought 3/06
1969 GTV - sold in '72, hope you're still OK.
"I've shot 630 elephants and 63 men, and I regret the elephants more." Arthur Jones.