The ABCs of RC Airplane Fuels – Best Gas You Can Use
This guide explains the basics of RC airplane fuels and their fuel systems. Mistakes in any area can result in a host of issues. The plane won’t fly as well as it should do in a best-case scenario. It may suffer a dead-stick landing at worst. Dead-stick landings happen when the craft loses its propulsive power. Common reasons for this are fuel starvation caused by leakage or poorly set up fuel systems.
The 5 RC plane fuel essentials covered in this guide include the following:
- Fuel systems: tanks, fuel lines, clunks, filters, and pumps
- Glow (nitro) fuel ingredients explained
- Understanding fuel blends
- Safe practices
- Buying nitro fuels
This easy-to-read guide is primarily for the novice or a refresher for more experienced pilots. The rest of this page refers to the fuel as nitro for consistency.
#1 RC Airplane Fuel Systems
Your radio-controlled model airplane needs a radio system and a power system to fly. Nitro-burning aircraft risk dead-stick landings if they lose fuel or fuel supply prematurely. A typical fuel arrangement includes the tank, fuel filters, fuel supply lines, and fuel pumps. A poorly set up fuel system can result in the aircraft engine smoking, misfiring, or not even starting.
RC Plane Fuel Tanks
Choosing a fuel tank can be overwhelming for those building a custom RC plane for the first time. Model aircraft tanks come in many shapes, sizes, and builds. The key here is to follow the seller’s recommendations—that’s it. Even kits that don’t include tanks will likely suggest a commercially viable option. Check user reviews or ask in RC forums if you’re unsure.
- No history of splitting or cracking due to pressure or vibration
- Screw on-caps stay firm and have no history of leaking
Leaking nitro fuels is a nightmare you want to avoid. Fuel oil is a messy business if it soaks into the wood of a model plane, and it’s impossible to completely clean. It can also weaken any glued joints and potentially damage parts of the radio gear. Also, consider fuel barbs on the ends of the inlet and vent lines. Barbs are a quick and affordable way to prevent fuel hoses from sliding off.
Fuel Lines (Hose)
Most RC fuel lines for nitro engines are the flexible silicone variety. The most common issue RC pilots have is with lines that slip off. The good news is that it’s an avoidable problem with a little care. Barbs or simple zip ties are the way to secure these lines from the tank to the carburetor and muffler.
Fuel lines come in the following four sizes:
- Small: Used for 1/2a—10 engines
- Medium: .15–.60 engines
- Large: .90 and up
It pays RC nitro enthusiasts building a fleet of planes to invest in spools of line.
Fuel Tank Clunks
Another thing worth knowing is the fuel tank clunk. The clunk refers to a short piece of tubing inside the tank with a heavy weight at the end to keep the tube in line with gravity. Why is this so vital? Well, model RC planes fly at all angles, experience G-force, and do fancy acrobatics in the air. All these maneuvers move the fuel around, and the less there is, the more space it has to swoosh.
The clunk arrangement is a simple yet effective way to keep the fuel tube submerged in nitro fuel. That means the aircraft won’t suffer from fuel starvation during its flight.
RC Airplane Fuel Filters
The two RC airplane filters are fuel and air. The job of a fuel filter is to prevent dirt clogging up the carburetor. The air filter stops dirt from reaching the engine. RC fuel filters are inexpensive and vital for the optimal functioning of any nitro-powered aircraft. RC air filters are harder to come by, so you may have to improvise. Some RC’ers use a patch of nylon stocking over the carb.
Filters are not optional if you want full protection for your model plane. Always filter the fuel from the jug to your fuel tank. Ask at community forums if you need help with creative air filter ideas.
Nitro Fuel Pumps
RC nitro-powered planes typically use two kinds of pumps. One takes the fuel from the storage can and puts it in the plane’s fuel tank. These are simple fueling pumps. The other pump takes fuel from the tank and delivers it to the engine. They are the engine fuel pumps.
Some pilots prefer manual pumps to get fuel from the can to the tank. These simple devices use a type of squeeze bulb and are ideal for filling smaller models. Electric pumps are better for larger tanks.
The job of an engine fuel pump is to maintain a consistent flow of fuel to the aircraft’s engine. It’s more critical with scale models that perform lots of high-speed aerial aerobatics. Not all RC planes need engine fuel pumps, though, so it’s not a good idea to fit one for the sake of it. After all, it’s one more mechanical component to maintain and potentially break.
#2 RC Airplane Fuels
You now have a basic understanding of the RC airplane fuel system. This next section looks at nitro fuels in more details and the things you need to know to get the right blend for your aircraft.
Not all RC airplane fuels are equal, so a little knowledge helps to get things right. Some call it RC glow fuel even though it has no ‘glow’ properties. Others refer to it as model or nitro fuel, but it’s the same stuff even though it comes in several blends. It’s crucial that RC plane pilots choose the right fuel.
Glow Fuel Ingredients
RC model aircraft fuel is a special blend of three main ingredients and minor additives. There are several blends of nitro fuel available. Each one is suited to different types of engine and performance requirements. The 3 primary ingredients used in RC nitro fuel include:
- Methanol (also methyl alcohol, carbinol, wood alcohol, and others)
- Oil (synthetic or castor)
These are the ingredients that provide the plane with the power it needs to fly. Now let’s break each one down to see why it’s such a necessary component.
The Job of Airplane Fuel Ingredients
Methanol is the primary, sole explosive ingredient with two functions. 1) Methanol ignites with a platinum glow plug. This reaction keeps the plug red hot and ‘glowing.’ 2) Methanol releases tremendous energy—more per pound than that produced by gasoline.
Oil is also a vital ingredient and can be either castor or synthetic. Oil lubricates the moving metal parts and thus protects them from wear. Castor used to be the most popular choice for model aero engines. It’s a natural with better lubricating qualities than synthetic oils. Despite that, it’s not perfect.
Castor oil leaves a sticky residue that goes hard if left unattended. So, routine maintenance is necessary to prevent engine damage. That’s why more pilots now prefer low-maintenance synthetic oils. Most off-the-shelf glow fuel blends use synthetic oil with a small percentage of castor oil.
Nitromethane is where the word ‘nitro’ comes from. It’s a ‘hot’ fuel that works as an oxidizer. An oxidizer is a chemical that fuel requires to burn. RC planes only need a small amount of nitromethane as its too hot and powerful to use in any large quantity. It’s also highly explosive and needs handling with great care. Drag racing is a perfect example of the volatile properties of nitro fuel.
Additives: Some RC plane fuels contain small percentages of additives. These are typically rust inhibitors and an antifriction component of some kind.
Choosing the Right Nitro Fuel Blend
Choosing the right fuel for your RC gas-powered aircraft is not difficult but needs to be right. A lot of problems are the result of wrong fuel mixtures used in ignorance. Only skilled enthusiasts should experiment with fuel blends. Everyone else should follow the engine maker’s recommendations until they have more experience. Then—and only then—is it safe to dabble with different blends.
An RC plane fuel blend relates to the amount of each ingredient. We refer to the exact concentration of each element in percentage terms. Fuel blends affect the performance of an aircraft in different ways. That’s why there’s no single blend to suit all models. Engine type, i.e., 2-stroke or 4-stroke, also determine fuel choices. The table below gives a rough guide of ingredients and percentages:
|Nitro Fuel Ingredient||Uses||Percentage|
|Nitromethane (Nitro)||General sports type flying||10–20% (15% typical)|
|Oil (natural or synthetic)||General sports type flying||15–20%|
The table is only a rough guide and leaves plenty of room for experiment.
Any flammable substance needs careful handling. Refer to the manufacturer’s instructions on how best to care for and store the product. The shelf life of nitro fuel is quite long, but it can go off. Improper storage is the main culprit here with moisture contamination being the biggest threat. The problem with methanol is that it readily absorbs water molecules from the atmosphere.
If water gets into your fuel—even in tiny amounts—it’s finished. A quick check inside the storage container and its lid should tell you if water has gotten in. Discard the fuel if there’s any sign of condensation no matter how slight. Moisture can get in if you use the wrong type of container. More common reasons are a broken lid or one that’s not screwed down tight.
Here’s a recap on the ways to protect and store nitro fuel:
- Always refer to—and follow—the manufacturer’s guidance
- Always store at room temperature in a dark space
- Always use a purpose nitro fuel container
- Always check and double check the lid is secure
Buying Nitro Fuels for RC Planes
Buying RC airplane fuels is easy and the safest way for newbies to proceed. There are lots of places to get hold of prepared blends in various size containers. Below are three examples:
PowerMaster Nitrofuel, 20%, 1 Quart | Compatible with all RC vehicles that use 20% nitro fuel
Torco RC Fuel, 20% Nitro 1 Gallon | Compatible with RC car, boats, truck, planes, and helicopters
Torco RC Fuel 15% Nitro airplane 1 Gallon | Compatible with all RC aircraft that use 20% nitro fuel
It’s tempting to be ambitious and want to experiment with blends from the outset. After all, tweaking and fine-tuning is half the attraction of flying gas-powered RC aircraft. Even so, slow is always the best approach. Getting experience from the bottom up is a guaranteed way to make you a better pilot. Start with the fuels and engine settings recommended by the plane’s manufacturer.
It never takes keen enthusiasts long to get familiar with it all. You have plenty of scope to experiment with nitro blends. First, you need to know how different fuel combinations may affect the performance of your RC plane. You’re only ready to test when you know what you’re trying to achieve—specifically.