Tractor Gas
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=31417
Printed Date: 10 Mar 2025 at 5:53am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Tractor Gas
Posted By: TedBuiskerN.IL.
Subject: Tractor Gas
Date Posted: 28 May 2011 at 1:37pm
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Just got a 1969 180 gas running good. It had not run in six or seven years, but was in a shed. The book calls for 91 research octane gasoline. Is that the same as the octane listed on the pumps at the service station? On the pump it has a formula of R+M/2. I assume that is Research + M???? divided by 2. I drove it to town and put 93 octane Shell in it. Does this tractor need high octane gas at 8.25 : 1 compression?
Someone who knows help me out here. ------------- Most problems can be solved with the proper application of high explosives. |
Replies:
Posted By: Jeff Z. NY
Date Posted: 28 May 2011 at 1:46pm
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Probably not at that compression ratio.
The R+M/2 method is just a tricky way of posting good numbers on the pump since it's and average between two octane rating methods. |
Posted By: Jeff Z. NY
Date Posted: 28 May 2011 at 1:50pm
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PS: Right, "R" for research method.
That will not be the number on the pump. |
Posted By: Jeff Z. NY
Date Posted: 28 May 2011 at 2:04pm
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I'm not sure since it's been along time ago since my racing days but I think one test is a high speed test and the other is a low speed test and the standard now is to average them to get the bests of both worlds for the engine at all speeds.
I don't remember, it's been along time since I messed with gas octane ratings. I can't even remember what the test chemical was but I could never pronounce it anyway. |
Posted By: dadsdozerhd5b
Date Posted: 28 May 2011 at 4:27pm
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do yourself a favor and run the high test. it will run better and store longer if you are not working it hard. also has less or no ethanol in it to go bad faster. i have had alot of funky things happening with carburators that have never been a problem before even with stabil in them. ------------- HD5B, HD5G, (2) FARMALL A's, CUB. DO IT RIGHT THE FIRST TIME, IGNORE THE LAUGHTER. FLANNEL IS ALWAYS IN STYLE. |
Posted By: 427435
Date Posted: 28 May 2011 at 5:03pm
Actually the opposite is true. If you run E10 gas all the time, you'll have less storage problems. If the old gas tank has a bunch of water and crud in the bottom of it, the first tank or two of E10 could be a problem as you clean that stuff out. Once cleaned out, the E10 will keep your tank and carburetor free of standing water. It's the cleaning out process of old shellac buildup in the carbs that can be an issue referred to above but, once clean, the carbs stay clean with E10. Contrary to all the old wives (shade tree mechanics) tales, E10 is the way to go. I've just restarted my boat, MH, 2 garden tractors, a lawn mower, and an old chain saw after they sat all winter with E10 in the tanks. The garden tractor and lawn mower tanks weren't even full. Everything started up and ran well. ------------- Mark B10 Allis, 917 Allis, 7116 Simplicity, 7790 Simplicity Diesel, GTH-L Simplicity Ignorance is curable-----stupidity is not. |
dadsdozerhd5b wrote:Posted By: Lonn
Date Posted: 28 May 2011 at 9:25pm
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I used to think Ethanol in the gas was good but in my experience you will have carb problems if the engines sits a few months also when I bought my chain saw the Stihl dealer said to try not using ethanol. I never had so much trouble with bad rotten fuel until the ethanol showed up. In the car it's fine cause it gets used nearly everyday. ------------- -- --- .... .- -- -- .- -.. / .-- .- ... / .- / -- ..- .-. -.. . .-. .. -. --. / -.-. .... .. .-.. -.. / .-. .- .--. .. ... - Wink I am a Russian Bot |
Posted By: Gerald J.
Date Posted: 28 May 2011 at 9:34pm
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M is for motor method. In the motor method of testing for octane they use an engine with adjustable compression ratio. They increase the compression ratio until it begins to ping, then they mix octane (a hydrocarbon) and some other standard low octane rating hydrocarbon until the engine knocks the same. The octane rating of the fuel being tested is the amount of octane hydrocarbon needed in the standard fuel to get the same ping or knock. I'm not sure of the Research method, its probably a chemical analysis and the two methods hardly agree. So pumps tend to show the average of the two. Gerald J. |
Posted By: Brian Jasper co. Ia
Date Posted: 28 May 2011 at 9:42pm
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I've been using E10 in my gas tractors with no problems. They don't get a lot of use and don't have any carb problems either. When I filled each one last summer, I did put Stabil in them. ------------- "Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford |
Posted By: BrettPhillips
Date Posted: 28 May 2011 at 10:04pm
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The "R" stands for "Research", meaning that the Research octane number is found through chemical based lab testing. The "M" stands for "Motor", meaning that the lab uses a special engine with variable compression that is mounted on a dynamometer to arrive at a "practical" octane number that is based on real-world knock tendency in a controlled environment. The R + M / 2 method just takes the average of the two numbers to arrive at the number that is on the sticker at the pump. In other countries I understand that it is common to see only the Research octane number, or RON on the pump. Since the Research octane number is generally higher than the Motor octane number, you would probably be fine to use 87 or 89 R + M / 2 octane gas. |
Posted By: 427435
Date Posted: 28 May 2011 at 11:55pm
Again, what you are struggling with is either water that was already in your fuel tanks or old shellac being removed from your fuel system by the E10. Clean your carburetors and drain your tanks if necessary. As I posted, I haven't had a fuel problem in years and I have 3 vehicles, 3 air-cooled engines, and a 60' vintage McCullough chain saw that sit for months and then fire up with no issues (other than possible dead batteries). ------------- Mark B10 Allis, 917 Allis, 7116 Simplicity, 7790 Simplicity Diesel, GTH-L Simplicity Ignorance is curable-----stupidity is not. |
Posted By: TedBuiskerN.IL.
Date Posted: 29 May 2011 at 2:26am
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Thanks guys, looks like the 87 R+M/2 with 10% ethanol would be OK to use, and about 15 cents a gallon less costly here in N.IL. than the 93 octane.
This tractor may be for sale in the future. Runs like a top, now, everything seems to work, I even got all the lights working. Straight sheet metal, show 93xx hours on tachometer which still works. Has a fuel issue I need to work out yet from sitting so long, line plugs occasionally. Rear tires like new, left front OK, right front will need to be replaced before long. Tire guy comes Tuesday to fix a small fluid leak before it ruins the rim. Still needs a new seat, but for now a boat cushion will have to do, got bills to pay first. ------------- Most problems can be solved with the proper application of high explosives. |