high octane gas in super m

some people say that an old gas tractor will run alot better with 93 octane instead of 87, is this true? does 93 give you any more power or is it a waste of money. ive heard that you can tweak your carb differently for more power when using 93 is this true?

Save your $$ and get the cheap stuff. Shoot these tractor where made to run on the cheap stuff any way and just think about how many where made to run on distalite which was as cheap as you could get and still burn. Now ya if you mill the head and put in dome pistons and a bunch of other thing you might need to get the high price stuff but not in a stock M

There are a lot of old wives' tales about 93 octane gas... More power, runs better...

Heck, I've even heard that the higher octane replaces the lead in gasoline... It doesn't.

The compression in the old (pre '06 series) 4-cylinder IH gas engines is not high enough to require high octane gasoline.

Gasoline will ignite with enough heat and compression. This will manifest itself as a "ping" in a gasoline engine... I'm never quite sure about the whole relationship between pre-ignition, spark knock, and ping. They may be the same thing, or maybe not, but I'm pretty sure they all stem from the gasoline igniting before the spark plug fires.

What octane does is basically "stabilize" the gasoline so it doesn't ignite too soon in high-compression engines. The gas goes bang when it's supposed to go bang...

Agreed.

An M has around 7:1 compression, 87 octane doesn't become an issue in even the most extreme situation until you reach 8.5:1 compression. If you are getting pre-ignition its not your gas.

Don't know with your tractor as old said it . In my S/MTA that is what i run with the M&W flat tops i do not have the plug fouling that i had with the 87 it runs cooler on the 93 . Do you have to on them don't know myselfbut on my buddy Vernon's S/MTA yea ya have to with the high alt. pistons and the 450 head . We all just get the high test and if it is gas powered then that is the gas that goes in . We have a couple 706 gassers and they HAVE TO feed on the 93 or ya guild pistons or melt them .So we have one tank of 500 gal. for diesel on the one farm and a 300 gallon for the gas and at Vernon's place there is a 1000 gal diesel tank and a 500 gallon gas tank . Our fuel supplier brings us good 93 octane gas at both places. a few years back they hired a new guy to drive the fuel truck and he brought a load of gas that was wrong out and filled the tank at Eugene's . Eugene filled the 706 up backed into the barn hooked up to the grinder mixer pulled it to the corn crib and started to grind a batch of feed and was working the 706 like we always do when grinding and promptly ate a piston . The new driver had brought out a load of 87 and not the 93 that he was suppose to . They paid for the repairs as they know what can happen to the pistons on the 87 , i also built the owners son two pulling tractors .

My stepson and I did a science project together for school on this subject about five years ago.

We used a stock M (with gas head)....used 87, 89, and 93 octane...and ran three different ignition timings... We used a 1 gallon gas tank instead of the stock gas tank.

The dyno results actually showed a lose in horsepower using 93 octane.

Pre igntion is flame initiation prior to spark. Causes are from compression heat, Poor octane fuel, a glowing combustion chamber deposit or overheated tip of sparkplug. Spark knock is from advanced timing, or poor octane. It is caused by early plug spark for that gasoline, or correct timing in low octane fuel.
If a flame front is initiated too soon, the trapped mixture is still being compressed as the piston approaches TDC. The heat and pressure of the progressing flame super heat the remaining unburnt fuel/air. this allows it to detonate (combust through its volume all at once, not burn with a flame front. Compare a firecracker to lighting a trail of gun powder with a match)
This detonation causes Knock/Ping sound.
Modern computer controlled systems listen to each cylinder and adjust timing to produce the tinyest knock. This is not harmful as it is just barely present. The timing thus set produces the greatest Peak pressure in the chamber just as the piston goes past TDC (5 degrees or so), and burns more of the remaining fuel that would normally have quenched out. Todays cars' CPUs learn timing from those sensors and adjust to each cylinder to talior combustion efficience, and adjust for differences between each tank of fuel. Jim

Save your money!

In engineering school I did dyno testing of various gasoline grades in an early 50’s Jeep flathead 4 and a 60’s Chrysler slant 6. (Both engines have compression ratios similar to a Farmall Super M).

The differences in power and fuel economy between 87 regular and 93 premium were less than the limit of experimental error. (If I recall the premium actually delivered a bit LESS power)

We also tested several aviation gasolines: red (87 octane), blue (100 octane low lead) and green (130 octane ) with similar results.

We learned also tweaking fuel mixtures and timing would make no power improvments when using higher grades.

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Bottom line: Go ahead and use premium if you wish – it won’t hurt anything. And the blue Sunoco premium looks pretty in the sediment bulb(!) But unless your Super M knocks at full load on regular, switching to premium benefits only your fuel supplier.