93 octane fuel in a low compression engine

[1Mech]

I recently bought an old International B-414 gasoline tractor, reading through the owners manual, I noticed it called for 93 octane fuel.
Now this is only a 6.3:1 compression ratio engine, why in the world would they recommend such a high octane fuel?
Was octane rated differently in 1963?

 

[3 Horse Ranch]

I think they changed the way they rated octane in the 1970s with the advent of catalytic converters and unleaded gas. My best guess is that modern regular octane gas will be more than sufficient in your tractor.

 

[Jims1025R]

Octane ratings were changed some long time ago, now being "research octane number" (RON) + "motor octane number" (MON) / 2. That said, I cannot imagine any reason that a 6.3:1 engine needs anything greater than the least octane rating gasoline you could possibly find. I have done octane testing on airplane engines from 7:1 to 9:1 compression. 7:1 runs happily on 80 octane, which is no longer available as an aviation gasoline, the 9:1 runs happily on 91 octane.

It is possible, though I think unlikely, the the tractor engine manufacturer wanted some tetra ethyl lead (TEL) = "leaded gasoline" through the engine, knowing that higher octane gasoline used to have lead. You're out of luck with that in any [auto gasoline] case. The lead lubricates the valves a little, but not enough that I'd worry about missing it. If you want to be ultra conservative and run some lead, go to your local small airplane airport, and buy 5 gallons of 100LL aviation gasoline - it still has a fair amount of lead, and is 100 octane. Mix a little in with your regular unleaded autogas. When I used to run auto gasoline in my airplane (which was approved), I would try to get one tank every 20 tanks of 100LL just to get a little lead into the gas for the valves.

Your greater risk will be the effects of ethanol, which is probably mixed into the gasoline you're buying. It has a lesser energy density that pure gasoline, and ethanol may attack some of the non metallic components in the fuel system. Again, low risk, but not none...

If in doubt, run the auto gasoline you can get, and keep the RPM up, and the load down on the engine - rather than lugging it at low RPM. If detonation is a risk (which I very much doubt anyway) it's less a risk at higher RPM, low load, than the other way around....

 

[Roadworthy]

Check the stations in your area - internet is the easy way. Use a search term like no alcohol gasoline near me. If you don't use the tractor a lot that could be a good way to go. Alcohol retains water and can corrode metal parts it contacts (fuel line, carburetor, etc.) but it can also destroy older rubber or neoprene lines. Neoprene has been reformulated to deal with that. Many of the newer cars have plastic fuel tanks and fuel lines.

 

[Quebecguy]

I recently bought an old International B-414 gasoline tractor, reading through the owners manual, I noticed it called for 93 octane fuel.
Now this is only a 6.3:1 compression ratio engine, why in the world would they recommend such a high octane fuel?
Was octane rated differently in 1963?

I have an International 354 which is a similar tractor to yours although a few years younger in which I've been using regular gasoline since it was new. I suspect the motor in mine is pretty much the same as yours and I've never encountered any problems which I can attribute to low octane gas. Out of curiosity I've just checked my Owner's Manual and can find no reference or suggestion whatsoever as to recommended octane level so it can't be very critical!

 

[big bubba]

agree with the above consensus. you have a great old school machine, & i'd go the extra effort of locating non ethanol fuel just as i do for my small engines & old school truck. w/stabilizer additive, you engine will last forever. around here, non ethanol usually is premium 91, looking at your original question. i see no prob w/higher octane, along w/benefits of non ethanol.

 

[Richard001]

You definitely do NOT want to use gas with Ethanol in it. It will destroy your carb O-rings and gaskets. Locate and buy the 91 octane fuel and ad some of the additives that are designed for older engines that originally used leaded fuel.

Your pockit book will thank you.

Richard

 

[1Mech]

Thanks for all the replies, I am bringing it home from Missouri on Monday. The previous owner said it had a VW carburetor on it, he was using a "choke cable" on it, direct throttle control, so I need to get the proper carb and the governor linkage, which is currently not connected. Also need to loosen up the non power steering a bit, check for oil in the steering box.

 

[Williy]

Not sure but think you can purchase a lead additive from Wally world

willy

 

[mo1]

I recently bought an old International B-414 gasoline tractor, reading through the owners manual, I noticed it called for 93 octane fuel.
Now this is only a 6.3:1 compression ratio engine, why in the world would they recommend such a high octane fuel?
Was octane rated differently in 1963?

My educated guess is IH simply wanted it run on regular road gasoline.

The octane rating on the pump was different in the '60s, it was the research octane number like most of the rest of the world continues to use on their gas pumps. The octane number you see on the pump in the U.S. today is the average of the research octane number and the motor octane number. The current octane number is usually called "pump octane" but is formally called the "antiknock index". The research octane number is usually about 10 or so points higher than the motor octane number for automotive gasoline, which would put 93 RON gas at about 88 pump octane.

Your International B-414 was tested by Nebraska in 1962 and they used a regular leaded gasoline with a research octane rating of 92.2 and a motor octane of 84.6, for a pump octane of 88.4. Leaded regular was usually 88-89 pump octane between the early 1960s and when the EPA banned it at the end of 1995. The octane of regular unleaded gasoline today is very close to the octane of regular gasoline available in the '60s. The current mid-grade 89 is at least as high as the regular back then and modern 93 octane premium is not terribly far from what most leaded premium available back then ran, which was usually about 94-96 pump octane.

The main issue with running modern unleaded gasoline in an older engine that originally was designed to run on leaded gasoline is exhaust valve seat recission if the valve seat wasn't hardened and the engine is run hard for a lot of hours. I don't know if IH did hardened valve seats in 1962 or not. Almost everything made after 1970 or later did but as there was "white gas" . I would not worry about the small amount of ethanol in modern regular unleaded, just use the tractor with some regularity to not let the fuel go stale, which is excellent advice no matter what fuel your tractor runs on.