Even if you are not interested in mixing your own nitro fuel, you can still benefit from having more intimate knowledge about what is found in nitro fuel.
This can help you improve the performance of your RC model. It can even help you in extending the life of the nitro engine significantly.
What is RC nitro fuel made of? RC nitro fuel (also known as glow fuel or model fuel) is made of methanol, nitromethane, and oil. RC nitro fuel is made of methanol (between 60% to 80%), nitromethane (between 5% to 40%), and oil (between 8% to 25%). Fuel dyes and other fuel additives can sometimes also be found in nitro fuel.
As you will find in this article, not all nitro fuel is created equal, and there are some important details that you need to be aware of. And manufacturers may not always tell you the whole deal. So let’s take a look.
What Are the Ingredients in RC Nitro Fuel?
Generally speaking, there are two types of RC models when it comes to their power source—electric or battery-powered and fuel-powered RC cars.
While battery-powered RC models are powered by a battery and have an electric motor, fuel-powered RC models have fuel tanks and engines that run on fuel.
Most RC models have a two-stroke engine that runs on nitro fuel. Nitro fuel is made of methanol, nitromethane, and a lubricant, and it is also known as glow fuel or model fuel. It is the type of fuel most RC model cars, trucks, boats, planes, and helicopters use.
Methanol is a type of alcohol. It is used in the preparation of fuels, antifreeze, and some solvents. Originally it was derived from wood, but today it is made from natural gas. This is why it is also known as methyl alcohol or wood alcohol.
Methanol is the main ingredient found in nitro fuel, and it provides the bulk of the power output and the main reason why the fuel burns.
Methanol has a very low flash point of 52 to 54 °F, which means that it gives off ignitable vapors at those temperatures. The autoignition temperature of methanol, on the other hand, is fairly high or 878 °F.
This low flash point makes methanol a serious fire risk if not stored properly and not handled with care. The fact that methanol burns with an extremely pale blue flame that is nearly impossible to spot during daylight makes it even more dangerous.
Nitromethane is a colorless oily liquid and has some very interesting properties.
Nitromethane has its own nitrous oxide and oxygen atoms. Because of the extra oxygen, it can be said that nitromethane, to a certain degree, can replace the oxygen needed for burning fuel.
As a result—although nitromethane is not as powerful as gasoline—you can pump a lot more nitromethane in the cylinder generating more power. On average, you can pump up to 2.5 more fuel, but The increase in power is not too extreme.
Nitromethane has a flashpoint of 95°F and an autoignition temperature of 784 °F.
Nitromethane is used for several reasons:
- It keeps the engine running smoother and improves idling.
- It helps the fuel burn quicker, translating into more power and higher rpm.
- It makes for easier tuning of the engine in some instances.
That being said, the use of nitromethane is not mandatory. Using too much nitromethane can lead to excessive wear of the engine or overheating.
Some kind of a lubricant is necessary for the majority of RC nitro engines simply because they are two-stroke. Lubricants are added to the fuel mixture used in two-stroke engines to keep their internal parts in good working condition.
However, not all types of oil can be used. For a nitro engine, you need an oil that has good viscosity at low temperatures, mixes well with methanol, and does not burn at high temperatures so that it can retain its lubrication qualities.
When it comes to nitro fuel, the most commonly used lubricant is castor oil or synthetic oil. Castor oil provides better lubrication but leaves a residue inside the engine that should be cleaned; otherwise, it will accumulate and gum up the engine. On the other hand, synthetic oil will generally leave less residue, but its lubrication is not as good.
Sometimes a mixture of castor and synthetic oil is used in order to get the best of both worlds.
Fuel Dyes and Additives
Some manufacturers may choose to add other additives like anti-foaming additives, anti-corrosion, and degumming agents.
Usually, nitro fuel is clear and does not have any color. However, many manufacturers will also add fuel dyes to their nitro fuel. They do it for safety purposes or due to local regulations. For example, in some countries, it is required by law manufacturers to dye some types of fuel.
Usually, nitro fuel can be found in different colors like pink, red, green, blue, or yellow, but other color variations can also be found. The color itself does not affect the nitro fuel in any way. However, some manufacturers may choose to use different colors for nitro fuels with different nitromethane content. That being said, there are no hard and fast rules when it comes to nitro dying.
Fuel dyes and additives are usually in negligible quantities.
Ingredient Ratios in RC Nitro Fuel
The ratio between the three main ingredients in nitro fuel can vary a lot depending on various factors.
- Methanol content in nitro fuel will usually vary between 60% and 80%.
- Nitromethane content is typically between 5% to 30%, with 20% being the most common. However, nitromethane content can be as little as 0% or as much as 65% in some instances.
- The oil content in nitro fuels is usually between 8% to 25%.
What Is the Right Percentage of Nitromethane?
Between 20% to 30% nitro is used in most RC nitro engines. The 20% nitro fuel is considered the standard and best in terms of maximizing the engine’s life.
For casual use, you can go with a fuel containing 20% nitro or less. This will guarantee good engine life and decent performance all around. For racing, you want to have more power. This is why racers will usually move on to nitro fuel with more nitromethane in it, typically at least 30% and less oil. This will ensure more power and speed but can decrease the engine’s life. (Keep in mind that most places usually have rules as to how high your nitro percentage can be while racing.)
However, if you change the ratios of nitromethane, you have to retune the engine. You have to ensure that the engine will work within reasonable temperature ranges, doesn’t overheat, and that the detonation occurs at the right time to prevent engine knocking.
On the other hand, RC planes, due to the way they work, will often use fuel with a lower amount of nitromethane—about 5%.
In certain cases, they can even drop the nitromethane content down to zero. Some returning may be necessary and replacing the glow plug, too, but this is also a good way to save money.
Generally, you should not stray too far from what is recommended in your user’s manual. Ideally, you should stay within 10% of what is recommended.
The size of the RC nitro engine also matters. (RC nitro engines can vary between 0.07 to more than 0.36 cu. in.) Usually, on engines up to 0.18 cu. in., most people will not use more than 20% nitro.
What Is the Right Percentage of Oil?
Some engines are designed to work with specific nitro fuel that has certain amounts of lubrication.
If you run fuel with a higher nitro percentage, but lower oil percentage can lead to more wear and tear and significantly reduce the engine’s lifespan.
On the other hand, some store-bought nitro fuels are not really suitable for all nitro engines and can damage them. The issue stems from the fact that different brands will use different nitromethane to methanol to oil ratios. Some nitro fuels can, for example, have so high oil content that they can end up doing more harm than good.
So this means that you need just the right amount of lubrication for your particular use and RC vehicle.
For most nitro RC cars and trucks, people use between 8% to 12% oil. Full castor oil or a mix between castor oil and synthetic oil are generally good choices, while full synthetic oils are usually not as good and more corrosive in the long run.
Usually, RC planes will run at higher RPMs, so they work better with higher oil content. RC planes will perform better with fuel, which has 12% to 20% oil content.
Running too much oil in an RC car can negatively affect its performance and tuning capability and even clog the nitro engine. With the right amount of oil, the RC vehicle will start easier, and the idle will be smoother.
Initially, for engine break-in, you can up the oil content up to 15% for RC cars and 25% for RC planes.
Unfortunately, sometimes manufacturers will only list the nitromethane content and omit the oil content, which presents a serious problem when knowing how important the oil percentage in nitro fuel can be.
What Is the Right Percentage of Methanol?
Most people will start by deciding how much nitromethane and oil they need and then just top up with methanol.
Usually, after determining how much nitromethane and oil should the nitro fuel contain, the rest up to 100% is reserved for methanol. So if you have 20% nitromethane and 10% oil (20%+10%=30%), methanol is going to be 70% (or 30%-100%=70%).
This is why methanol content will vary wildly. It can go between 60% to 80%, especially when no nitromethane is used.
Can You Make Your Own RC Nitro Fuel?
Preparing your own nitro fuel can be super fun and an excellent project to do in your free time. Nonetheless, you are dealing with highly flammable and toxic agents, so extra caution is advised.
One question that you may be wondering is, why would you want to mix your own nitro fuel in the first place?
Here’s the thing.
Usually, people that can source the ingredients locally will find that making their own nitro fuel is cheaper and allows for more versatility. On the other hand, if you have to pay for shipping, it will not be worth it as it will end up being just as expensive as store-bought nitro fuel, if not more.
How Much Does It Cost to Make Your Own Nitro Fuel?
A gallon of 20% to 30% nitro fuel costs, on average, between $30 to $60.
Pure nitromethane is usually very expensive. A gallon of nitromethane is around $50, while pure methanol is usually fairly cheap. It can cost about $7 per gallon. Oil can also be an expensive ingredient costing about $50 to $100 per gallon. Generally, making your own nitro fuel can cost about $20 to $30 per gallon.
Generally, buying the individual ingredients and mixing them yourself can end up being 20% to 30% cheaper than buying preblended nitro fuel.
What You Need to Make Your Own Nitro Fuel?
All you need to make your own nitro fuel is pure methanol, pure nitromethane, and castor oil. The other things you would need are a few measuring cups, a funnel, and a container for storing the nitro fuel.
Unfortunately, depending on where you live and your local regulations, you may not be able to purchase directly pure methanol or nitromethane, which leaves you with the only option of buying premixed blends from your LHS.
Do not use regular two-stroke oil as it does not mix with methanol and nitromethane. Using regular two-stroke oil in a nitro mixture will usually ruin the whole batch unless the two-stroke oil you are using has explicitly been specified to blend with nitro fuels.
How to Calculate the Ingredient Ratios
Calculating the amount of nitromethane to methanol to oil you need to use is very easy to do once you know the formula needed.
Usually, the best way to go about this is to prepare 1 gallon of nitro fuel. We know that 1 US gallon equals 128 ounces. So if you are going to prepare fuel that contains 20% nitromethane, you need to find what 20% of 128 ounces is.
The formula is 0.20 × 128 = 25.6 oz (or you need 25.6 oz of nitromethane per 1 gallon of nitro fuel).
Then you need to find how much oil you are going to use. The amount of oil is calculated with the same formula; all you need to decide is what percentage of oil you want to use.
For example, for 15% oil, the formula will be 0.15 × 128 = 19.2 oz (or 19.2 oz of oil per 1 gallon of nitro fuel).
Now that you have the nitro and oil figured out, you need to find how much methanol you need to add in order for everything to come up to 1 gallon in total. So far, in this example, we have used 20% nitromethane and 15% oil, which gives us a total of 35%. The rest up to 100% will be methanol or 100% – 35% = 65% of methanol. (The percentages of all three ingredients should add up to 100%.)
The formula is the same as above; you only change the percentage. This gives us 0.65 × 128 = 83.2 oz (or 83.2 oz of methanol per 1 gallon of nitro fuel).
Alternatively, you can add the amount of nitromethane and oil (in oz) and deduct that from 128 oz. So we get, 128 oz – (25.6 oz + 19.2 oz) = 83.2 oz.
To make sure our calculations are right, all we need to do is add the three ingredients together and see if we end up with 128 oz (or 1 gallon of fuel).
25.6 oz (nitromethane) + 19.2 oz (oil) + 83.2 oz (methanol) = 128 oz (or 1 gallon of fuel).
How to Make Your Own Nitro Fuel?
The good news is that all you need to do is mix methanol, nitromethane, and oil, and you end up with nitro fuel. It really doesn’t get any simpler than that, but caution should be exercised at all times. (Don’t forget you are dealing with extremely flammable and dangerous liquids.)
When mixing your own nitro fuel, it is recommended to start with the oil first. Keep in mind that the oil is very thick and viscous, so it will take some time for all of the oil to pour into the container and fully wash off the measuring cup and funnel.
Now add the nitromethane to the oil. The oil and the nitromethane will not mix immediately, so close the container and give it a good shake to force the nitromethane and the oil to mix. If you leave the nitromethane and oil mixture to sit for a while, it will separate again—this is normal. Once you add the methanol, everything will mix and dissolve properly.
Just measure and add the methanol you will be needing. Add the methanol to the nitromethane and oil mixture. After you have added all of the methanol, close the container’s lid and give it a good shake again until everything dissolves nicely, and you end up with a homogeneous mixture.
Make sure to wipe dry any spills.
Due to the nature of the agents used, homemade nitro fuel can sometimes vary in quality and ingredient ratios. This is one reason why manufacturers will often use computers during the manufacturing process, which ensures the fuel is of the best quality and has the same ratio of ingredients.
How to Dye Nitro Fuel?
Since nitro fuel is clear in color, some hobbyists will want to find a way to dye it for safety purposes. Dying your nitro fuel also helps you see how much fuel is left in the tank and the gun.
Adding one to four drops of food coloring to a gallon of nitro fuel is usually what most people do to dye nitro fuel. However, food coloring is water-based. And although many people have tried and tested running RC cars with nitro fuel dyed with food coloring and have never experienced any problems, it should be noted that it could create rust and corrosion.
That being said, most people consider a few drops of food coloring to a gallon of fuel to be relatively harmless, especially if you run the engine dry each time.
Ideally, you want to use fuel dye that has been specifically created for dying nitro fuel. Talk to your LHS and see if they can offer you a suitable product.
Do the Ingredients RC Nitro Fuel Is Made of Go Bad?
Now let’s take a look at whether the different ingredients in nitro fuel and nitro fuel itself will go bad over time.
- Methanol is considered to have practically indefinite shelf life if stored in a sealed container. However, if methanol is not stored properly, it can absorb water, get contaminated, and the methanol content can start slowly evaporating over time.
- Nitromethane can also slowly degrade over time if not kept in a sealed container out of direct sunlight.
- Oil can start degrading when exposed to temperature swings and moisture. In most cases, the oil should stay good for several years if stored properly.
This means that nitro fuel does go bad with time. Generally speaking, nitro fuel has a shelf life of 12 months once opened. However, it can go bad sooner, depending on how it is stored. If the nitro fuel has been kept out of direct sunlight, has not been subjected to temperature changes, and the container has been kept sealed, it can stay good for several years.
Is RC Nitro Fuel Dangerous?
You should exercise extra caution whenever working with nitro fuel because nitro fuel can be dangerous.
Extra care is advised, particularly if you are mixing your own nitro fuel.
Methanol is extremely dangerous and toxic, and since it can burn with a virtually invisible flame, it is a serious fire hazard.
Methanol is non-drinkable, and the consumption of even small amounts of it (as little as 10 to 30 mL) can lead to metabolic acidosis, blindness, and death. In addition to that methanol, inhalation is also not safe. It can lead to a burning sensation in the nose, hot flashes in the area of the head, headaches, confusion, and more.
Methanol is highly toxic and can be absorbed through the skin as well. Methanol fumes are also toxic and a health hazard.
Nitromethane, on the other hand, is not considered as dangerous and toxic as methanol. Nonetheless, it still is a health and a fire hazard if not handled properly. Nitromethane and its fumes are highly toxic and known carcinogens as well.
When it comes to oils, you can stumble upon both highly toxic and less toxic oils, so generally speaking, their use should also be handled with care.
Because of that, while mixing or handling nitro fuel, it is recommended to use proper protection. Wear protective latex gloves, safety glasses, and a face mask (or a respirator).
Can RC Nitro Fuel Be Substituted?
Now that you know what nitro fuel is made of, you may wonder if nitro fuel can be substituted or made with different ingredients.
When running on 0% nitromethane, some people will add about 3% acetone, which is considered to be equal to about 5% nitromethane. Acetone is primarily used for improving the starting and idle. However, acetone is not used as a complete substitute for nitromethane.
But most people will wonder if they can run their nitro engines with regular gasoline.
Nitro engines can be converted to run on gasoline. That said, gasoline should not be used in stock RC nitro engines as it is more powerful and produces more heat as it burns than nitro fuel. As a result, gasoline will cause the engine to run hotter and may eventually destroy it.
Much like gasoline, diesel also cannot be used as a nitro fuel substitute. Diesel requires specific compression and is not going to ignite in a standard RC nitro engine. However, even if diesel could ignite, it would give off a lot more heat as it burns, which would cause the engine to overheat.
WD-40 is one of the agents that can be used as fuel in RC nitro engines. To use WD-40 as fuel, you have to mix it with regular nitro fuel or methanol. So WD-40, on its own, is not a viable substitute for nitro fuel and can damage the engine.
Some engines can start and run on ethanol (also known as Denatured alcohol or ethyl alcohol) instead of methanol. Ethanol and methanol both act similarly. Still, ethanol has slightly different properties than methanol, so comprehensive testing, tuning, and modding should be done to ensure the engine works properly, but it could, in theory, be made to work.
Overall it comes down to how nitro engines work. The glow plug in the engine has been carefully designed to ignite the nitro fuel at the right time and moment. Any drastic changes will usually affect the smoothness and effectiveness of how the engine works.