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Do You Need to Use Race Gas and Fuel Stabilizer

Fuel Considerations for Pit Bikes​

Pit bikes generally perform adequately on premium pump fuel, provided there is no audible pinging under load. It is advisable to use fresh 91+ premium fuel. Additionally, incorporating a fuel stabilizer like Sta-Bil can prevent jet clogging and ensure smooth operation.

Oxygenated fuels can enhance power output but come with drawbacks. They are not only expensive per gallon but also harsh on engine internals and highly corrosive. To mitigate these effects, it is recommended to run regular fuel through the engine after using oxygenated fuel.

When to Use Race Gas​

If your engine experiences pinging or you prefer using race gas, consider a fuel with the following specifications:

VP-110:

  • Type: Leaded/Non-Oxygenated
  • Usage: High-octane, leaded, non-oxygenated fuel

Understanding Octane​

The octane rating of gasoline is a crucial measure of fuel performance. Higher octane numbers indicate a fuel's ability to withstand greater compression before detonating, commonly referred to as "pinging" in motocross. High-compression engines require fuels with higher octane ratings to prevent detonation, whereas lower octane fuels are generally safe for most stock four-stroke motocross engines.

The engine's compression ratio dictates the necessary octane level. Modified engines often have higher compression ratios due to high-compression pistons or milled heads, which increase horsepower but also demand higher octane fuel to avoid pinging, leading to increased fuel costs.

Insights from Motocross Action Magazine​

Winning races involves pushing the engine to its limits. The more ignition and heat the engine can handle, the more horsepower it can produce. However, excessive ignition timing and heat can lead to engine failure. Racing fuels and high octane levels allow tuners to approach these limits safely.

Race fuel is not a panacea. While no single fuel can offer all benefits, understanding your performance goals can help you select a suitable fuel.

What is Octane?​

Octane measures a fuel's resistance to detonation, expressed as Research Octane Number (RON) and Motor Octane Number (MON). The pump number at gas stations is an average of RON and MON, known as the anti-knock index (R+M/2). Racing fuels often list the MON, as it reflects performance under heavier loads. Be cautious of advertising claims that highlight the RON, as it is typically higher, but the MON is more indicative of racing performance.

The Misplaced Octane Obsession​

There is a common misconception in racing circles regarding octane. Engines only require as much octane as necessary. A stock engine can operate efficiently on 91 octane fuel, and using 108 octane will not enhance speed. Excessive octane can lead to sluggish throttle response and incorrect burn rates, ultimately reducing power.

High octane fuels burn slowly, while low octane fuels burn quickly. This "burning speed" is crucial for optimal performance. The engine should reach peak cylinder pressure at 20 degrees after top dead center. If the fuel burns too quickly or too slowly, it fails to contribute effectively to the engine's power output. Selecting the appropriate fuel for your engine's setup is essential.

The Role of British Thermal Units (BTUs)​

Beyond octane, the energy value of fuel, measured in BTUs, is vital. One BTU is the energy required to heat one pound of water by one degree Fahrenheit. Racing fuels measure energy in BTUs per pound, not per gallon, as the air/fuel ratio is based on weight.

Practical Advice​

Most production motocross engines are designed to run on 91-octane, unleaded premium fuel available at local gas stations. If the engine can handle pump gas under race conditions without detonating, expensive race gas may not offer hidden power. However, certain race fuels can enhance power in non-detonating engines, particularly oxygenated fuels. Riders must decide if the cost is justified. Choosing the wrong fuel can result in power loss. Suitable fuels for stock engines include VPR, U-4.4, and T4, with MRX02 and MR12 offering more power at a higher cost.

Fuel Freshness​

Fuel freshness is as important as its composition. While non-oxygenated fuels can remain fresh for years in metal cans, oxygenated fuels should be used within a year to maintain their oxygen content. Fuel stored in plastic cans should be used within two weeks, as plastic is porous and allows the best fuel components to evaporate. To extend fuel life, transport it in plastic cans but store it in steel cans at home.