What gas should you use in your 1967 mustang?

For most classics, it is best to purchase the highest octane fuel you can find (91 or 93), if you can afford it.

I always try and avoid anything with ethanol in it (as most gas has nowadays). I can still find ethanol free gas at most marinas. I also occasionally use racing gas but my car has a high compression ratio. If you drive a lot you should also use a lead substitute additive in your gas to avoid valve damage.