You want to take your RC car out for a spin, but you’ve had that bottle of nitro fuel in your garage since last summer, and you’re not sure if it’s still usable. How’d you know if nitro fuel is bad? And how long does it last?
RC nitro fuel lasts as long as a year or more if stored in a dark, dry place with constant temperatures. Nitro fuel is a mixture of methanol and nitromethane, which breaks down over time. Using aged nitro fuel will run your RC car, but this leads to poor performance and engine wear.
If you’re wondering what to do with that old bottle of nitro fuel, or if you want to know how long your new bottle will last, you’re in luck. Strap yourself in and get ready to learn everything you ever needed to know about the fuel for your RC car!
How Long Can RC Nitro Fuel Last?
Many people change out their nitro fuel every year. If properly stored, RC nitro fuel can last for years. RC hobbyists report that 20 and even 30-year-old fuel still works fine, so long as it hasn’t changed its appearance or viscosity.
Can Nitro Fuel Go Bad?
If you leave the cap off your fuel bottle overnight, there’s a pretty good chance that it’s ruined. The methanol has undoubtedly pulled in enough water to cause idling problems and potentially corrode your engine. Consider your mistake an expensive lesson and replace the bottle with new fuel.
How Do You Know if Nitro Fuel Is Bad?
If your nitro fuel looks thick and gummy, or if you see water droplets condensing on the inside of the bottle, it has gone bad. Nitro fuel which is not quite so far gone can still cause you problems. Degraded nitro fuel will make your RC car run slowly and bog down frequently. The exhaust will be thick and smelly. If you notice these symptoms, stop driving immediately.
What color was the nitro fuel when purchased? If your fuel now looks cloudy or has changed color, chances are there has been significant chemical degradation. At best, your RC car will not ride as well: at worst, it might do active harm to your engine.
When in doubt, replace your nitro fuel. If it has been stored in poor conditions, you’ll generally do better erring on the side of caution. And when you get your new nitro fuel, be sure to keep it tightly sealed in a dark, dry place with a constant temperature.
What To Do When You Need New RC Nitro Fuel
Ideally, you should stick with the same type of oil once you have tuned your carburetor. If you cannot get the brand of nitro fuel you were previously using, you should find another brand with similar percentages of nitro and lubricants. Try to keep the ratios of the new nitro fuel within 5% of your previous brand.
NOTE: If that’s not possible, you’ll have to readjust your carburetor. A jump of 10% in nitromethane will require a leaner air/fuel mixture. A drop of 10% will need a richer mixture of air and fuel. Small changes in your nitro fuel formulation will generally cause you few if any problems.
Why I Need to Drain Nitro Fuel Before Storing an RC Car?
Before you put your RC car up for the season, you should drain the fuel. If left in storage, much of the methanol and nitro can evaporate. This oversight will leave you with a discolored mess in your tank when the summer arrives. And to make things worse, nitromethane degrades into nitric acid, which can corrode your engine’s metal.
Often you can solve this problem simply by siphoning out the tank and adding fresh fuel. You may also have to change the fuel lines, air filter, fuel filter, and glow plug if contaminated with oxidized fuel. Or you may find yourself soaking your engine in mineral spirits to remove gummy residue.
How to Drain Nitro fuel in RC car properly?
- Empty your tank before you put your car up.
- Run your engine dry, then pull the fuel feed line and attempt to start the engine.
- Squeeze a few drops of after-run oil such as the Liberty Oil 100% Synthetic Lubricant (available at Amazon.com) into the open carb, then detach the glow driver and turn the engine over for a few seconds.
After you have prepped the engine, look over your car and see that everything is still in working order and securely attached. A bit of time spent on maintenance now can save you a lot of heartaches when spring comes, and you want to take it out for a drive.
Tips for Proper RC Nitro Fuel Storage
All three of nitro fuel’s main ingredients can go bad if improperly stored. Here are some tips on how to store your nitro fuel properly:
- Keep your nitro fuel tightly sealed and stored in a dry location, as methanol draws moisture from the air.
- Choose a storage location that will maintain a steady temperature. Big temperature swings can cause some oils used in nitro fuel to degrade more quickly.
- Keep in a dark place. Nitromethane degrades in direct light, and if kept in light too long, most of the nitromethane will break down.
Keep in mind that both nitromethane and methanol will evaporate over time. If you store an RC car over the winter with fuel in the tank, you may wind up with an oily mess in your engine when summer comes.
What are RC Nitro Fuel Components?
There are many different brands of nitro fuel (also called “glow fuel”) available. All of those brands of fuel have three primary ingredients, which I describe below.
The differences between brands lie in the ratios and the fuel’s intended use. Some nitro fuels are intended for boats and airplanes. Some brands mix their nitro fuel with competitive RC car racing in mind. Still other nitro fuels aim at the general use hobbyist market.
Methanol Is Nitro Fuel’s Main Ingredient
Methanol, or methyl alcohol, has more energy per pound of air than gasoline and is easy to ignite. When added to gasoline, methanol produces a cleaner-burning higher-octane fuel. Methanol makes up over 60% of every commonly sold brand of nitro fuel today.
Your RC car will run on pure methanol (Don’t try this, though! The performance will suffer, and ultimately, your engine will too!). The other ingredients add performance and lubrication. Methanol powers your RC car’s engine.
Lubricants Keep Your RC Car Running Smoothly
Unlike your automobile, RC cars don’t come with a crankcase full of oil. Their engines rely on lubricants in their fuel to keep running smoothly. Most nitro fuels sold today use a mixture of castor bean oil and synthetic oils.
Nitro fuels include different amounts of lubricant depending on their purpose. When castor oil was the primary lubricant, lubricant percentages typically ran around 18%. With the advent of synthetic oils, 7% to 12% is more typical. Racers usually use a lower rate of lubricants in their nitro fuel, leaving more room for nitromethane.
Nitromethane Gives Nitro Fuel Its Name
Drag racers and RC car hobbyists use nitromethane to increase their fuel’s power output. But nitromethane burns at over 4,000°F (2,204.44°C). Mixing it with methanol helps keep the ignition cool enough to run without burning up your RC car’s engine.
Nitro fuel comes in many different formulations. RC car racers use nitro fuel with nitromethane percentages of 30% or higher. They are looking for speed and expect wear and tear on their cars. Hobbyists will do better with a lower-nitromethane fuel. 20% is considered a good number for general use.