stumper Well-Known Member Joined Jul 22, 2011 Messages 1,879 Reaction score 48 Location North Carolina Feb 26, 2012 #51 71dartswinger said: I have a owners manual for a 71 Mercury and it calls for reg gas for 302/351/400 at 91 octane 429 2v and 4v premium at 99.8 octane 1971 octanes were different than today's ? Click to expand... Maybe a manual for a foreign country car (Australia ?) There are different ways to calculate Octane numbers.
71dartswinger said: I have a owners manual for a 71 Mercury and it calls for reg gas for 302/351/400 at 91 octane 429 2v and 4v premium at 99.8 octane 1971 octanes were different than today's ? Click to expand... Maybe a manual for a foreign country car (Australia ?) There are different ways to calculate Octane numbers.
