I'm a little embarrassed to have to ask this (I'm just getting into collector cars and have a great deal to learn), but I'm not sure if I should be running prem. or reg. in my 302 engine. I just bought the car and it has a tired motor in it which is not the orginal. I had some work done on it by someone who knows his stuff and the compression is bad spitting oil out the dipstick. I'm going to have the engine rebuilt this winter but I was wondering, in the meantime if I should be running prem. Since I bought the car, I've been running prem and I have never heard the engine knock. Thanks for advice!
you only need to run the octane level that doesnt ping in your motor. your just wasting your money if you run premium and the motor doesnt ping on regular. i sugest on your next fill up puting in just a few gallons of regular and go drive it. if it doesnt knock then stay with the reg. if it knocks then try midgrade. if that knocks then you know that you need premium. most 302s that ford made were made to run on 87 so chances are you will be fine with 87
Regular fuel was 89 octane in the late 70's. Lower octane fuel burns faster and hotter than higher octane. Back in the mid 90's I wrote a program to figure out the cost differences of mpg vs price of buying premium gasoline. I got more mpg from using premium gasoline but it cost me .0007 cents a mile...in other words I saved .0007 cents per mile by buying regular gasoline. Your mileage my differ. A clogged PCV will also cause you to push oil through the dip stick.
Most stock 302's will be fine on 87, especially one that's tired. My 200 runs better on 87 then it does on 93.
Premium fuel actually burns slower than regular... it is part of how it controls pinging. This means more carbon build-up in the long run. As a motor carbons up, it can create more pinging due to hot spots. So ... running premium in a motor that didn't need it in the first place means that you might need to run it all the time as the motor ages, where you could have been running regular all along and have cleaner chambers. The 351 in my car has stock compression and a rowdy cam. Both are good for lower octane requirements. A bigger cam will bleed off some cylinder pressure at lower rpms where a motor is prone to ping at. Another factor is ignition timing. I can run 89 octane in it under all conditions. If on a long run on the highway, I will drop to 87. Ultimately, like others have stated, run the lowest octane the motor is happy with.
In '69, regular octane was rated at 93 octane and premium was 97. Premium at some point was 100. Remember the old Sonoco 260? Of course, this was also leaded fuel. I believe the ratings changed in '72 or '73, after the government stepped in. Jim
my original owners manual says 92 I agree with them, try to drop it and see if it pings. also altitude can make a difference, i have to run lean so i have to be careful about temps. pinging also means running hotter, running too high of octane can actually make it harder to get leaned also. its like a balancing act over 4k feet
