Gas for a 656

Manual says to use 93 octane. Highest farm gas I can buy here is 89 octane. I checked a bottle of octane booster at the store
and all it said was add to 20 gallons to boost the octane. You guys know how much a bottle of octane booster will raise the number
on the octane of 89?

Thanks for your response.

Does your local gas stations have higher octane. Local here has 91 to 93 octane.

Yes. I can buy 91/93 at the corner, no lead. Farm gas has modern day lead substitute I'm told.

(quoted from post at 03:10:29 09/14/17) Yes. I can buy 91/93 at the corner, no lead. Farm gas has modern day lead substitute I'm told.

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Yes, everyone who has the 6 cylinder IH gas engines needs to know they will not run properly on the 87 octane gas available today. I found that out a number of years ago when my 656 gas gear drive was fouling plugs and would start missing on one or more cylinders. It also ran rough. I saw a thread on RPM about this and decided to try the super high 91/93 octane gas here at the pumps. What a difference that made and the tractor now runs smoothly with no plug fouling. It also starts easier. So I checked the operators manual and sure enough the manual states the 91/93 octane rating is what is needed. The 91/93 octane gas is quite expensive but is not a big issue as I only put about 50 hours per year on this tractor. I also might say that my B414 gas and Super C run ok on 87 octane but then their compression ratio is lower at around 6.5 to One.

According to the fuel data in Nebraska test report #909 the 656 was run on 88.8 (R+M)/2 octane gasoline so what you have available is good enough. The 93 octane recommendation in the manual would be the Research rating, not the (R+M)/2 ratings we have now.

I bought a new 656 gas in the fall of 1966, it ran good on the lower grade of gas, that fall, the next spring i took my basic training, and my brother used it,wouldn't pull the next spring! But what was the grades back then, wasn't etyhel gas, 102 octanes then ?

Don't worry about the lead. Lead additives are just snake oil. There is no lead in them. They do nothing, and the lead is not necessary anyway. These engines have hardened valve seats already.

I asked the same question here about 6 months ago. The results were similar to asking a question about what oil or trans/hyd fluid to use; quite a few differing opinions.

I have a 656 gas with a freshly rebuilt engine and have been running 91 octane no ethanol gas in it since the rebuild. A few hundred hours on the engine now. All I can say is it starts & runs great on that gas. Yes it's a hit in the wallet but worth it IMO. Peace of mind is worth something.

Someone should tell our 656 that it can't run on 87 octane, it still gets about 800 hours a year on it. The 263 only has at best a 7.5:1 compression ratio. If your plugs where fouling and you generate a miss its not the octane of the fuel you are running - in fact the lower octane would probably help with that. Higher octane fuel is actually more difficult to ignite (the whole point of higher octane).


The manual refers to RON octane rating, todays fuel is rated on the average of RON and MON octane ratings.

You were told wrong. The closest thing to a "lead substitute" is ethanol.


http://www.slate.com/articles/health_and_science/the_green_lantern/2011/03/ethanol_nitrogen_mtbe_lead.html

Your comment about higher octane gas being harder to ignite is WILDLY WRONG. As long as the air/fuel ratio is within the proper range low octane and high octane both start easily. What is different about high octane gas is there is a series of chemical reactions that have to happen before the air/fuel mixture combusts and the reactions take longer in high octane gasoline than in low octane gas. When the air/fuel mixture combusts cylinder pressure goes thru the roof, with enough heat and pressure the whole combustion chamber full of fuel/air can explode which you can hear as pinging or detonation. The longer time the high octane gas has reduced the ability of heat and pressure to cause this explosion, the chemical reaction only allows the fuel to burn so fast in a wave thru the combustion chamber. The detonation from low octane gas can blow head gaskets, collapse piston ring grooves on pistons, burn holes in pistons, burn valves, some say it even accelerates wear on conn rod bearings. The cylinder pressure spikes are HUGE!

Same BTU per gallon between low and high octane, so mpg, or work done per gallon or hour is the same. Tetra-Ethyl lead is still available in race gasoline, 104-108 octane. I've run a blend of 1-1/2 to 2 gallon race gas to 5 gallon 91 or 93 straight non-ethanol no-lead and it was like it was 1964 all over again with good leaded high octane gas available at every gas pump. Some guys run 100 Low Lead aviation gas in their gas tractors, I called my local airport and it's Painfully expensive, more than I pay for race gas for sure.

I use about 100 gallon of 91 octane no ethanol Recreation gas a year to mow the lawn with every year, and about 20 gallon a year in tractors to move snow. If I farmed and burned lots of fuel everything would be diesel.

You say I am wildly wrong, the actually repeat what I said only with less efficiency. I can sum up your post with one sentence.


The purpose of the high octane is to reduce or eliminate pre-detonation when compression alone could cause the fuel air mixture to combust before spark is applied.


Basically you kind of repeated what I said only with a lot more words. High octane fuel does not burn (or "explode") as easily as low octane fuel. In the case of the poster I was responding to he was having an issue of detonation not even happening - which would have little to do with octane levels being discussed.

Of course your 656 will start and run on 87 octane. The question is, how long will it last?

If you've got a well worn engine with the old original forged pistons in it, you're probably fine. A fresh engine with the cheap cast pistons you can only get now is ripe for melting a piston due to detonation from low octane fuel:

http://www.misterfixit.com/deton.htm

I am NOT getting into this one as you ALL know where i stand on this and i can guarantee that i have worked on more I H gassers then any of you on here and i know what todays gas does when working one . NOW IF you are running 4-560 and down and not updated 656 and UP and even the 504and the 544 4 cylinders you can get by with PUMP gas . so 1963 and up to the last gassers need the good stuff and today ya ain't going to find the good stuff . at this time we now have two 706 gassers with pistons melted . We did use them to farm with every day . And i am done replacing junk pistons with junk pistons .

Thank you for putting your comments out on this topic. Your points need to be emphasized, and I never tire in reading them. I think back to the 806 gas we had on the farm. I was pretty young when it left the farm and we moved on to diesel engines, but I remember hearing about the issues we had with the gasoline delivered to the farm. It was imperative this tractor had high octane gasoline. The lead was slowly coming out of the gasoline and the octane ratings were dropping. The results were the 806 would suffer from pre-ignition as a result if the gasoline was not high enough in its octane rating. Keep us in line, Tractor Vet!

I run 91 in my MH, it is 9.5 :1 compression.

I'm just speculating here but I wonder if there are oil pull-over concerns with the 6cyls (???) I don't know anything about the ring tension or the process used to finish hone the cylinder bores. But, engine oil in very small amounts kills octane rating of fuel faster than anything.

I can see (have seen!! :shock where you have a big problem if you start knocking in an automotive engine at 5krpm but these tractor engines are nowhere close to that amount of crank speed.



:idea: aftermarket piston cooling oil jets :lol: