RC Plane Fuel Guide: Glow Nitro, Gas Mix and Storage

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Fuel is where combustion RC planes most often go wrong. The label on a jug of glow fuel shows a nitro percentage that gets all the attention, while the oil, the plumbing and the storage habits decide how long an engine lasts. Gasoline engines add a different set of questions about octane, ethanol and the oil ratio.

This guide is based on engine manuals, maker pages and the US National Institute for Occupational Safety and Health (NIOSH), not on our own bench work. Prices are left out because they change often, and stock was checked in October 2026. Where the sources disagree, the engine maker's manual comes first. Electric power systems are covered elsewhere, in the motors guide and the LiPo guide, and the gas vs electric guide compares the three power systems.

Quick reference

How glow fuel works

Glow fuel is three ingredients. The Evolution Engines manual puts it plainly: "The largest portion of the fuel is methanol (alcohol)." Nitromethane is added in a stated percentage, and the rest is oil. The label's big number is the nitromethane content, not the whole story.

Nitro: follow the engine maker

The makers' numbers are narrow. The Evolution manual recommends "high quality Cool Power Omega, Hangar 9 AeroBlend or Power Master fuels containing 10 to 15% Nitro", says the engine was test run with those fuels, and warns that "if another brand of fuel is used, it may be necessary to slightly adjust the needle valves to compensate for the differences in fuel."

Saito says almost the same thing in its glow manual: "For maximum protection and longevity of their engines, Saito recommends a fuel containing 20% oil and 10-15% nitro methane." If that blend is not available, the next best choice is "a high quality 2-cycle glow fuel", with the Hangar 9 Aero-Blend, Omega, Cool Power, K&B and Power Master brands named as examples.

Higher nitro belongs to engines whose makers call for it, and the manuals read for this guide do not. The practical reading of the manuals is simple: start in the 10 to 15% range for a sport or trainer engine unless the manual says otherwise, and treat a change of brand or nitro percentage as a reason to recheck the needle settings. The glow plug guide covers the plug side, and the engine troubleshooting guide covers problems.

Oil: the number that protects the engine

Saito is specific about oil. Its glow manual recommends 20% oil, says "use of fuels composed entirely of castor oil is not recommended", and says that "a mix of synthetic-castor oil is acceptable". Its list of tips for longer engine life starts with "use a high-quality fuel containing 20% lubricants". Oil content therefore matters at least as much as nitro, and a fuel that is much lower in oil than the manual calls for is a risk.

Car and truck fuels are formulated for a different duty cycle, and nothing in the engine manuals suggests substituting them. Use fuel sold for airplane engines.

Fuels in stock

When checked in October 2026, Horizon listed these glow fuels:

• Morgan 15% Cool Power with 17% oil, quart, in stock. Horizon quotes the maker's claim that Cool Power has been proven for more than 40 years.
• Morgan 10% Omega fuel with castor, quart, in stock.
• A 10% Omega control line fuel, in stock.
• VP Racing's YS/Saito 20/20 fuel and its 10% RC aviation fuel with 18% oil were out of stock.

Stock for glow fuel is thinner than for most hobby supplies, so it is worth checking before planning a flying day around a particular blend.

Gasoline and oil mix

Gas engines are spark-ignition and do not use nitromethane. The main questions are the gasoline, the oil and the ratio.

Gasoline

The Saito gasoline manual calls for "a mixture of high-quality 91 octane unleaded gasoline and a reliable, high-quality 100% synthetic oil for 2-cycle engines". It states that fuel with up to 10% ethanol "has been tested and found to work fine". Other makers do not specify octane in the sources read for this guide, so the manual for the engine in the airplane decides.

Oil and ratio

The ratio is set by the maker, and the makers differ:

• Saito gasoline four-strokes: 20:1 "for break-in and continuous operation on all engines."
• O.S. GT15: 30:1 to 50:1, per Horizon's specification.
• Desert Aircraft: "Red Line Racing oil at a 40:1 ratio", with Motul 800 or Stihl HP Ultra as alternatives, and a warning to avoid oils designed for liquid-cooled motorcycle engines.

Saito also explains why its oil advice is so specific. With a 20:1 mix some carbon buildup on the exhaust valve is normal, and standard 2-stroke oil can cause "a build up of a gummy residue on the exhaust valve in a 4-stroke gas engine". That is the reason it recommends the Evolution oil (EVOX1001Q) or a comparable high-quality synthetic.

One of the more useful oils to know about is the Deluxe Materials PowerModel 2T-S, a full synthetic oil that Horizon listed in stock. The maker says it exceeds the JASO FD and API TC standards, blends with leaded, unleaded and oxygenated gasolines (about 20% ethanol), and is suitable for 3W, DA, DLA, DLE, MOKI, OS, ZDZ, Zenoah, NGH, MVVS, BME and Saito engines "at manufacturers recommended ratios", with mix ratios up to 50/1.

Oil per gallon

The arithmetic is simple. A US gallon is 128 fluid ounces, so the oil needed per gallon of gasoline is 128 divided by the ratio:

Those figures are our own arithmetic. The ratio itself always comes from the engine manual. The gas engine guide covers sizing and the engines that use these ratios, and the gas engine troubleshooting guide covers starting problems.

Tanks, tubing and filters

Fuel plumbing is a place where glow and gas differ in ways that matter.

• Tubing. The Evolution glow manual uses medium silicone tubing for the glow feed and vent. The Saito gasoline manual is the opposite: "DO NOT use a silicone rubber fuel line for the engine, the fuel tank, or your fueling system", and it names Evolution gasoline fuel tubing (EVOA102) as the recommended tubing.
• Tanks. The Du-Bro 408 8 oz tank holds 5 to 9 oz, has a one-piece clunk with built-in barbs and can be used with pressurized fuel systems. Du-Bro says it can be used with glow fuel or gasoline if the Cat. No. 400 gasoline conversion stopper is bought.
• Clunks and filters. Saito says a filtered or sintered clunk on the pickup line is required for gas, and that a reliable fuel filter (the Saito F-1, or the Hangar 9 Pro Fuel Filter) should be fitted because "commercial gasoline has many impurities." Du-Bro's tank filter 161 is a sintered bronze weight and filter, and its 340 in-line filter uses a 130 micron mesh. The Sullivan Crap Trap large has a 100 mesh Monel screen followed by a 120 mesh stainless screen, cleans by backflushing and is designed for glow, gasoline and diesel. All were listed in stock except the small Sullivan size, which was on backorder.
• Fill valves. Du-Bro's Kwik-Fill valves let the tank be filled without disconnecting the fuel line, and they come in separate versions: the silver valve is glow fuel only and the red anodized one is gas only. Its Fill-It system is described for glow fuel and gasoline.
• Pumps. The Hangar 9 Ultra Fuel Pump is a manual pump for gas and glow and was in stock.

Keep the two systems apart. Du-Bro sells its glow and gas valves as separate products, and Saito's rule against silicone tubing applies to the whole gasoline fueling system.

Storage and shelf life

The Evolution manual gives the clearest storage advice for glow fuel.

• Methanol is hygroscopic, meaning it "attracts moisture", and water in the fuel "will cause poor engine performance".
• Sunlight eventually breaks down the nitromethane.
• A semi-translucent plastic jug can condense moisture inside it, and Evolution says "the only way to overcome the greenhouse effect is to store your fuel in a metal can."
• Squeeze extra air out of the container at the end of the day, or move fuel into smaller containers, and bring only a quart or half-gallon to the field.

Signs that fuel has gone bad, per Evolution, are the inability to start at previously used needle settings, a poor idle, bogging during run-up and failing to reach previous rpm.

For gasoline, the Saito manual says to store fuel in a clearly marked, sealed, water-resistant container in a cool, dry place away from children, and not to let fuel containers sit directly on concrete, "as the fuel may absorb moisture".

After the session

Both Evolution and Saito stress after-run care for glow engines. Saito recommends an after-run oil when the day's flying is done. Evolution says that if the engine will not be used within 10 days, about 10 drops of after-run oil should go into the carburetor and the engine should be turned over for a few seconds. For long-term storage, Saito says to drain the tank and the engine, remove the glow plug and put several drops of light oil in the plug hole and down the pushrod tubes. The beginner kit guide and the ARF, RTF and PNP guide explain the starting points for engine-powered builds.

Safety

Fuel is a hazard, and the sources agree on the basics.

• Methanol. NIOSH lists inhalation, skin absorption, ingestion and skin or eye contact as routes of exposure, a flash point of 52 F, and a recommended exposure limit of 200 ppm as a time-weighted average with a skin notation. Its emergency card says the odor does not give enough warning of low levels of exposure. Gloves, ventilation and no ignition sources are the sensible response, and glow fuel should be kept away from sparks and heat, as Saito's manual says.
• Gasoline. Keep it in a clearly marked container, away from children, and beware of carbon monoxide fumes in a closed space, as the Saito manual notes.
• Starting. Keep face and body out of the propeller's path, avoid loose clothing, and secure the airplane before starting, per the same manuals.

Turbine fuel

Turbines run on a different fuel altogether. AMA document 510-A limits fuels to kerosene, diesel and propane unless approved in writing, and requires two fuel shut-off provisions. The turbine engine guide covers the engines, and the giant-scale guide covers the big airframes that use larger gas engines.

Which fuel to use

• A glow trainer or sport engine. The maker's recommended blend, typically 10 to 15% nitro with around 20% oil for Saito, from an airplane fuel. The trainer guide lists planes designed for these engines.
• A four-stroke glow engine. Follow the manual. Saito asks for a synthetic-castor oil package.
• A gasoline engine. The maker's gasoline grade and oil ratio. Saito: 91 octane, 20:1. O.S. GT15: 30:1 to 50:1. Desert Aircraft: Red Line at 40:1.
• A new engine. Follow the break-in instructions, which are usually richer and slower.

Frequently asked questions