I've got the opportunity to purchase a 1978 Buick Reagal 3.8l, What octane fuel are these designed to run on?
Good afternoon. My apologies for the late response. From what I've read online the manual recommended a minimum of 87 Octane. Inherit benefits of using mid grade, premium octanes or additives are speculative as to whether or not there is a benefit.
Jim, I hope this helps. If you have any more questions please feel free to ask. Don't forget to rate my response to you.