Premium vs mid and regular gas

[Paul]

I just finished walking my trusted Labrador Retriever and while walking him I was thinking about the various posts on here about people running regular gas and mid grade. I realize I may be flamed for this but I am going to say this anyway and hopefully somebody can clear this up in my mind.

The owner's manual for a '65 clearly states to run regular gas. I forget the exact octane but I think it says either 92 or 93 octane which was regular back in the 60's. Now I understand you can retard the timing and run just about anything you may want to. Why would you want to do that? Why not have the timing set where it really wants to be and run the recommended octane? What are you talking about? Two or three dollars and tankful for a car that is driven part time by a lot if not most people.

I simply don't understand why not have the timing set correctly and the proper octane.

Okay I am ready to be taught!

[JonK]

I'm more focused on finding REAL gas and avoiding the ethanol junk. I plan to drive my car a lot as I did before teardown, pretty much daily so the diff. between 87 and 93 can add up. With the current difference in prices I'm looking at closer to a $5 difference per tank which adds up to a tank pretty quickly. My new motor is 9.7:1, with the timing retarded I will probably be able to run 87 for DD duty for work, when I want to hit the track I can turn the timing up and fill with 93 I'm hoping, basically adapting the car for use.
Jon

[aslan]

There are some threads about this. Also don't forget that the owner's manual is about 47 years old. What was true then about gas is not necessarily true today.
Stan

[Paul]

I should have said that I am not including ethanol gas as I only run non-ethanol. I wasn't really thinking about built up engines as that changes the formula altogether.

Surely the gas is not the same today as back then but octane should be the same.

The previous threads are what got me to thinking about this question.

[LSG]

Paul, do we know which rating system is used in the manual ? Are they using a Research number ? a Motor octane number ? or the now current R+M/2 method ? As Stan mentioned, the hydrocarbon stew we refer to as gasoline is very different now from 40+ yrs ago.

And why would one wish to avoid ethanol, if thats even possible ? In my area anyways, ( SW Michigan ), ALL of our gasoline contains ethanol. It really doesn't cause a problem. LSG

[rickgto]

True. Ethanol in itself is an octane booster.

[TEXAS67MUSTANG]

I just asked a very similar question on here a few days ago and ended up learning more about gasoline than I ever thought possible!

Here's the link in case you're curious:

Great Gas Debate

[GypsyR]

If you own a vehicle newer than about 1996, it retards the timing to compensate for less than optimum fuel by itself. It's likely you won't even notice. In extreme cases you might notice and it could even turn on the check engine light. But it's normally when within the engine computer's operating parameters to make decent use of fuel that has a lower octane rating that what it was designed to use as an ideal. When it does this you are also losing a certain amount of performance, overall operating efficiency, and even some gas mileage. Probably not enough mpg loss to offset the saved cash of cheaper fuel but it narrows the gap.
Retarding your vintage car's timing by hand is a crude version of doing the same thing, with even a narrower gap between money saved and reduced engine efficiency. You'd have to do back to back testing and calculate miles per dollar spent to see if you are actually achieving. IMHO, it just makes more sense to tune an engine for optimum performance and efficiency (for mild-engined street use these CAN go hand in hand) and feed it the fuel it requires. I've never been one to want to impress people with time slips and dyno sheets and I like to use low octane gas. Therefore I build my engines with a tad lower compression than many so they run happily on 87 octane. Other folks are more interested in the high performance and race side of the car hobby and have different goals. They should be ignoring this thread completely.
It's been hinted at in other discussions that if you just don't see the value in blowing a few extra dollars here and there to keep your classic car up to par you are likely in the wrong hobby. If you really really like your old Mustang, having to spend a few extra dollars to feed it a higher octane fuel shouldn't be an issue for you. Of course since we're all human, we are allowed to occasionally grumble about how expensive old cars can be. Also golfing, motorcycling, scuba diving, wives, etc, etc, no matter how devoted we are to them.

[MrFreeze]

Originally Posted by Paul

I should have said that I am not including ethanol gas as I only run non-ethanol. I wasn't really thinking about built up engines as that changes the formula altogether.

Surely the gas is not the same today as back then but octane should be the same.

The previous threads are what got me to thinking about this question.

Octane is NOT rated the same way today as it was in 1965. A T or C code engine will run quite happily on modern regular unleaded. Set your timing for 36 degrees total advance and run the lowest octane fuel that doesn't make you engine ping under load

MrFreeze

[Paul]

So I guess I can retard my timing and lower the octane, retard the timing and the engine will be happy.

Very interesting MrFreeze. I did not realize that octane was not rated the same as in the 60's.

Thanks all!!

[bartl]

Yes, Motor Octane was used in the '60's and I believe it is still used for aviation gasoline. I'd leave the timing at the factory spec and run regular unleaded. If you get pinging then try another brand first before fiddling with the timing. Your other choice is to add a bottle of octane boost at every fill up.

[wantaboss]

i just run non formulated gas and thats premium only around here

[Vince in Philly]

Can't remember offhand what octane is suggested in the owner's manual for my '68 289-2V, but I once did the math to compare 1968 octane ratings to 2012 octane ratings. Based on that exercise, I fill my tank with 91 octane gas now.