Understanding Fuel

By Pete Bergstrom, Horizon Engine Product Manager

Model engine "glow" fuel is made up of three key elements: methanol, oil and nitromethane. Many fuel manufacturers include other additives that are designed to solve any number of common problems that may occur with our fuel. But for now, let's only address the most common elements of the fuel and how you can care for your fuel to keep it fresh and stop it from going "bad." These steps will ultimately make your model engine operations easier.

Why would fuel go "bad"?

The largest portion of the fuel is methanol (alcohol). Methanol is hygroscopic; it attracts moisture. This can cause your fuel to be contaminated with water, which will cause poor engine performance. Additionally, the UV rays in sunlight will eventually break down the nitromethane if the fuel jug is stored in sunlight for long periods of time.

How can you tell when your fuel has gone "bad"?

The first indications will generally be the inability to start the engines at previously run needle-valve settings. Another clue might be that the engine has very poor idle, runs but bogs down tremendously during run up and/or will not attain the same RPMs you are used to.

How do I keep my fuel fresh?

If you have the opportunity, look for someone at a flying field on a sunny day who has a jug of fuel that is only ¼ full. What you may notice is that there are droplets attached to the top and sides of the fuel. This is the moisture in the air that is condensing inside the jug because of the greenhouse effect of the semi-translucent plastic jug. One way to overcome the greenhouse effect is to store your fuel in a metal can.

You can also combat the effects of the moisture in the air by squeezing all the extra air from your fuel container at the end of the day or transferring your fuel into smaller containers as the level of the fuel is reduced in your gallon jug. Many pilots will invest in half-gallon or quart-size containers and only bring that amount of fuel to the field on any given day. This allows their main supply of fuel to stay at home in a controlled storage environment, virtually insuring problem-free fuel.