Do you guys run? I've heard mixed opinions on it, some claim better fuel = more power, some claim it doesn't make much of a difference. Wondering what would really be best for my '66 390 (in the '73).

 

I run 87 octane, i don't experience any pinging with it, i can't justify the added cost of running 89 or 91 octane, it's just a waste IMO.

 

That's what I'm running right now, I don't experience any issues either. My timings set right for the altitude and all, and it seems fine. I couldn't really find a reason to justify a higher grade either, but had a few people tell me you'll get a power increase or slightly better mileage with a higher octane.

 

As long as you are using the fuel that is appropriate for your engine there is no advantage to running higher octane.
Higher octane doesn't increase power. All the octane number is is a rating of the fuels anti-knock quality. It doesn't have anything to do with the quality of the fuel or how much power the engine will produce.

 

That is true, I run 91 because my engine will ping otherwise. Typically ethanol is used to up the octane rating from mid grade to premium, this can actually result in a loss of power because the mid grade will have more gasoline in it. I believe this is because the ethanol burns a bit cooler than the gasoline. They have been going over this subject pretty heavily on the gearhead tv shows on weekend mornings.

 

A co worker told me to go to a specific gas station, he said they don't have ethanol in their gas, and he said he gets better mileage out of it, I have not tried it yet.

 

All California gasoline is E10, so you cant get any without here.

However my 1973, with the 302 required Premium Leaded when it was new, and said as much in the owners manual if I remember correctly. Something to do with the EGR valve that was required on California models etc...

So it all depends on the engine calibration, and the engine build.

When California went to all unleaded gasoline, my engine needed rebuilding less than 12 months after the switch for instance... I used regular unleaded.

 

I got a friend who's dad owns a gas station locally, and told me the same thing. He said he honestly see's more miles out of a tank from there, versus somewhere selling ethanol blends and that hes not just trying to sell it even though its a few cents higher than the chains. I honestly agree with him, I've started buying almost exclusively their when I can, and notice $20 of gas will get me a lot farther than gas from a Shell, or Giant or what not.

 

Well, I have not tried it yet. I just rebuilt my 300 I6 this past summer. I ran a few tank fulls through it, and now at 750 miles I checked and I am getting 13.3 MPG, which I thought was a little low.

Now I did not build it for fuel economy. It is a total stock original build, and MPG was not a consideration. Now with that said, I still would have thought a 300 I6 would have done a little better than that. I did check all tires and did inflate them to 35 lbs. (they went from 22-30 lbs).

Timing is on, vacuum is 17 hg, rebuilt Carter 1 bbl, C4 with fresh seals, filter, and fluid, fresh dino gear oil in rear with 290 something on the rear gears. I am rolling on new 235/75/15 on stock rims and stock mag wheel covers.

I am not a lead foot by any means, those days are long behind me.

I am hoping after more of a break in, to get closer to 15 MPG or more. Maybe I will try the fuel with out the ethanol to see what that does, after I see a leveling out from the minor adjustmens I am currently doing.

 

I run 87 in all of my trucks and regularly run Chemtool B12(in the right proportions of course) through the system to clean everything out. My 79 F150 with 302 that is bored and cammed up some I run a little bit of 89-93 though it ocasionally.

My old 1944 John Deere A I have with .45 over high compression pistons is stricktly 93 octane, runs like crap on everything else.