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Suspension Tear Down

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Fuel Options

Snowmobile Fuels Page

What is the scoop on using RFG in snowmobiles? Octane Ratings? What gas should I run? It says Ethanol . . can I safely run it? What is MBTE?

All good questions. When I was working as a mechanic in the Polaris and Cat dealership, it was right when they phased in RFG and oxygenated fuels. I was right on the front lines of this, calling the companies, reading and researching, and answering one heck of a lot of questions.

The EPA and other government agencies came up with RFG as a smog reduction plan about 10 years ago. The basic idea was to make the gas burn cleaner by using additive compounds with a higher chemical oxygen content, and to reduce or eliminate some of the more harmful chemicals like benzene.

They tried to accomplish this several different ways, the most popular was to add either MBTE or ethanol. MBTE has since been banned as a pollutant and carcinogen, and is not really relevant any more.

There are considerable questions to this day about the effectiveness of ethanol blend fuels. I personally maintain that it is not an environmental issue as much as a political one. It just so happens that ADM, Archer Daniels Midland, is both the number one ethanol producer and one of the top campaign contributors, with absolutely huge campaign contributions to key legislators.

Anyway, we are stuck with it for now. Almost any pump you pull up to these days says that the gas contains 10%ethanol. It is not just in the big cities, but regional.

Ethanol blends have three major effects in a snowmobile engine. It makes the engine run hotter, it washes the engine parts of oil with the alcohol blends, and it can damage the fuel system. All of these are critical.

As far as the engine running hotter, it was the manufacturers' recommendation to increase jet size one full size, for example, from a 320-330 main jet.

Now, before you make an appointment at the dealer, it needs to be said that most sleds come from the factory that much over jetted or more. Most of us are just fine without any change. The spark plug is the best indicator. You know the drill, cocoa brown. White is bad.

Stock sleds are usually ok, modified sleds need to tune for it.

I will state without any hesitation that I have never seen an engine burn down because of ethanol or reformulated gas. I became somewhat of a failure analysis expert over the years, and do know what I am talking about. I had many failed engines come in for repair, and quite a few wanted to blame the gas. Not one had a valid claim. Not one.

The ethanol in the gas has a negative effect on the lubrication on the engine. It is a solvent and a degreasing agent, and not an oils friend. Again, most of us do not have to worry. They took the ethanol blends into consideration when they came up with the TCW oil standards, and if you run a dealer oil or quality substitute, you are ok. Run lawn boy oil in your new Mach Z? You might get away with it, but my cash says no. Don't be a cheapskate! You paid big bucks to snowmobile, $7 a quart is just not that much money. Yes, I am a firm believer in dealer oil.

Octane . . . 87? 89? 93?
The first thing you need to do is check your manual. Some say 87 is ok, but in some engines it will detonate and smoke a hole in your piston. It varies by motor and compression.

Personally, I run 93. My engine is modified and the timing advanced. I can not afford the extra heat of detonation. I prefer by a long shot, Amoco premium 93.

I did encounter on one of the links below a statement that I can not verify. It said that the 87 was made from different stock than the 89 or 93, and is some really bad gas. They claimed that a power head lasted 3 times longer in one test on 89. Again, I can not verify this, but I do agree that the 87 octane gas is some real crap. Spend the extra buck a tank and get the good stuff.

Fuel systems
The new ethanol blends affect fuel systems in a number of ways. It will dry out rubber based o-rings and seals in the carb, and gaskets and diaphragms in the fuel pump. Newer machines aren't as affected because they are built for it. Older machines will see more split o-rings, dry intake boots, and such. It is not something that will make the seals fail in a tank or two, but more over time.

The big one that affects all of us is how fast it goes bad in the carb. The new gas is much worse for going stale and turning green in the carb. It takes less than a month before it starts breaking down. It is not the green goo yet, but it is lower in octane, and will give poor results.

It also turns to the famous green goo faster that the old gas. I have rebuilt a few thousand carbs since the 80s, and I could tell right away when they changed the gas.

I do not run or recommend any 'heet' type de-icer products. It very seldom works, and throwing that much iso into your 2-stroke just can't be good. I have heard some say it actually attracts water to the gas. If you have a frozen gas line, the right answer is usually to drain and clean the fuel system.

Overall, the new gas doesn't affect most of us that much, except it goes bad faster. Tuned sleds and older sleds need to pay more attention to it. Again, watch your spark plug color. Tan or cocoa brown is good, white is bad.

I recommend running dealer oil, quality 93 octane gas(unless the manual says otherwise), and a little squirt of stabil in each tank to keep it fresh.

If you have any questions on this or any other topic, feel free to e-mail me. I will help if I can. Here are a few links I found on the net that relate to this. statemants on rfg use

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