Model fuel is basically a blend of Methyl Alcohol (Methanol) and Oil with the option of Nitro-methane added to improve idling, acceleration and increase power. This additive is by no means essential and most modern glow motors run very happily on “straight” fuel. Methanol is the main ingredient, and provides most of the power. The oil in the fuel is the source of lubrication for the engine.
Oil is used to lubricate all of the moving parts in the engine. There is no oil sump in a 2 stroke engine. You can’t put oil into the engine and just add fuel so the oil must be mixed into the fuel.
For many years the oil used was Castor Oil, a product refined from castor beans. It’s the same oil that you’ll find in your local drugstore or chemist for medicinal purposes, but lubricating castor is specially processed to make it less gummy and with fewer solids than the medicinal type. Lubricating castor oil is not certified for human internal use so it must not be substituted for medicinal castor oil.
In most modern glow fuels castor oil has been replaced by some kind of synthetic oil. The synthetic oils are used for several reasons:
1) They are less expensive than castor oil.
2) They are less gummy than castor oil.
3) They leave less mess on the model than castor oil.
They are not “better” than castor but have different characteristics that are highly desirable. That said, for some “problem” engines a fuel with some castor can be an advantage because it lubricates better at model engine operating temperatures. “Sport” or “regular” fuels are usually 100% synthetic oil. These are the types of fuel you will be using for your trainer engine.
The inclusion of Nitro-methane is a subject for discussion with your tutor. Ultimate power output is rarely a major consideration for trainers so improved power output is not really important. The only justification for its inclusion is to help idling at low engine speeds. It is a relatively expensive additive so if not required, money can be saved by purchasing a fuel without Nitro or a low percentage content.
Storage and Care
DO NOT store your fuel in an unsealed container. Air will get into the fuel container allowing moisture in the air to be drawn into the fuel. Methanol has a very strong attraction for water so the two will mix easily and readily. Model fuel contaminated with water will cause the engine’s performance to suffer. Idling and needle set up will be affected, it will tend to run hot and, all in all, it will be difficult to run properly.
Model fuel should be stored at a constant room temperature ( if possible). In an area with wide temperature swings, any moisture in the air in the bottle will tend to condense out and get into the fuel. Also, some oils will degrade faster if they are exposed to wide temperature swings.
Model fuel should be kept away from light as much as possible, especially if it contains Nitro-methane. Light will cause the nitro-methane to degrade and after a while, the fuel will work just as if it contained no Nitro.
Model fuel will last quite a while if it’s kept in sealed a container. As you will be learning and hopefully getting in plenty of practice, there should be no real danger of exceeding the active life of your fuel.
Buying Glow fuel online is a very expensive option because of surcharges applied in certain countries on top of the postal charge. I strongly suggest that you try to source your fuel locally if at all possible. Most model shops keep stocks.