Vintage Mustang Forums banner


661 Views 1 Reply 2 Participants Last post by  G1967T
I looked up the specs for the "A" code 289 on the site (great site!) and read the following about it's octane requirements.

"premium. . . The federal government standard for a specific grade of gasoline, set relative to its octane number. Through model-year 1965, "premium" fuel was not less than 99.0 octane. For 1966, this was revised upward to 99.8 octane."

Now I know that hp numbers were calculated differently back then, how about octane numbers? Did stock factory cars require almost 100 octane out the door back then? Should I be mixing in a bit of airplane fuel when I fill up?

John Harvey

1965 "A" Code Convertible. "298" V-8 (It is way overbored), balanced, decked, milled, forged pistons and rods, high torque cam, toploader 4 speed, red with a white top (glass window), and a white interior with black appointments.
1 - 1 of 2 Posts
Octane rating is based upon the same assumptions, then and now. However, the way it is tested for today seems much different than when I went to an U.S. Army school to learn "petroleum, oils, and lubricants" testing including octane rating of gasoline.

99 Octane essentially means, that gasoline burns at the same speed as a mixture of 99 parts iso octane gasoline and 1 part benzene gasoline. Bottom line is the new premium fuels may knock, ping, and make your car overheat because that fuel burns to fast and "bangs" in the combustion chamber before everything is ready. Thus less spark advance or an additive. Higher compression also causes the fuel to burn faster, thus lower compression ratios in the newer cars. Computers and engine management systems can help burn the new stuff in higher compression engines and supercharged and turbocharged engines.

That's about all I know, I hope it helped.

1 - 1 of 2 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.