What is the Best Fuel for Chainsaws?

Last Updated on June 29, 2025 by woodcutter

When it comes to running a chainsaw efficiently, choosing the right fuel is just as important as using the right chain or maintaining proper tension. But with so many fuel options available—regular gasoline, ethanol blends, pre-mixed fuels—it’s natural to wonder: What is the best fuel for chainsaws? The answer depends on a few key factors such as engine type, performance needs, fuel storage, and even environmental impact.

Understanding Chainsaw Fuel

Chainsaws operate on two-stroke engines, which differ from the four-stroke engines in cars. Unlike four-stroke engines with separate oil and fuel systems, two-stroke engines require a mixture of gasoline and oil to lubricate the engine’s moving parts. This mixture is critical because there’s no separate lubrication system. Using the correct fuel mixture prevents engine damage, reduces wear, and ensures efficient operation. Incorrect mixtures can lead to serious issues like piston seizure, excessive smoke, or power loss.

Standard Fuel Mixture

The industry-standard fuel mixture for most chainsaws is a 50:1 ratio of gasoline to two-stroke oil, meaning 50 parts gasoline to 1 part oil. For example, mix 100ml of oil with 5 liters of gasoline. This ratio is recommended by leading manufacturers like STIHL and Husqvarna for both professional and consumer-grade chainsaws. Some older or high-performance models may require a 40:1 ratio, which uses more oil for added lubrication during heavy-duty tasks. Always consult your chainsaw’s owner’s manual to confirm the correct ratio, as using too little oil can cause overheating and engine failure, while too much oil can result in carbon buildup, spark plug fouling, and excessive smoke.

Choose the Right Gasoline

Selecting the appropriate gasoline is crucial for chainsaw performance. Here are the key factors to consider:

Octane Rating: Most manufacturers recommend unleaded gasoline with a minimum octane rating of 87 (RON). Higher octane fuels, such as 91 or 93, may provide marginal benefits for high-performance or professional saws, but they’re not necessary for standard models unless the engine is modified for higher compression. Using higher octane fuel than recommended doesn’t typically improve performance and may be a waste of money (Madsen’s Shop).

Ethanol Content: Gasoline with up to 10% ethanol (E10) is generally safe for chainsaws, as confirmed by STIHL for all their tools (STIHL Fuel Mix). However, ethanol can absorb moisture from the air, leading to fuel degradation and potential fuel system issues, especially during long-term storage. Ethanol-free gasoline is preferred for chainsaws used infrequently or stored for extended periods. Avoid high-ethanol blends like E15 or E85, as they can damage fuel lines, seals, and engine components.

Fuel Quality: Always use fresh, high-quality gasoline from reputable stations. Avoid fuel from stations that dispense multiple blends (e.g., E10 and E15) through the same hose, as this can result in inconsistent fuel quality. High-octane aviation fuels are also unsuitable for chainsaws due to their specialized formulations.

The Best Type of Gasoline: Ethanol-Free is Ideal

Not all gasoline is created equal, especially when it comes to small engines. The best fuel for chainsaws is high-octane, ethanol-free gasoline. Ethanol, commonly found in regular gasoline (up to 10%), can absorb moisture from the air and cause engine corrosion, carburetor damage, and starting issues—especially if the chainsaw is stored for long periods. That’s why premium fuel without ethanol (often labeled as “REC-90” or “ethanol-free gas”) is considered the gold standard for chainsaw longevity and performance.

Pre-Mixed Fuel: Convenient and Engine-Friendly

If you want to skip the hassle of mixing fuel and oil yourself, pre-mixed fuel (like those sold by Husqvarna, STIHL, or TruFuel) is an excellent alternative. These products are ethanol-free, perfectly balanced, and often include stabilizers to prevent degradation over time. While pre-mixed fuels are more expensive, they offer unmatched convenience and can extend the life of your chainsaw by ensuring optimal combustion and reduced carbon buildup.

Depending on your chainsaw’s usage, specialized fuel mixtures may be appropriate:

• Professional-Grade 50:1 Premixed Fuel: Premixed fuels like STIHL MotoMix or Husqvarna’s premixed fuel are convenient and ensure the correct ratio. They’re ideal for everyday cutting tasks and provide consistent performance while minimizing the risk of mixing errors (FarmstandApp).
• High-Performance 40:1 Ratio: This mixture, with more oil, is suited for heavy-duty tasks or older chainsaw models. However, it may lead to carbon buildup or spark plug fouling if used in saws designed for 50:1.
• Ethanol-Free 50:1 Mixture: Perfect for chainsaws stored for long periods or used infrequently, ethanol-free mixtures prevent fuel system issues caused by moisture absorption.
• Winter-Formula 50:1 Blend: Designed for cold weather, these blends improve starting and performance in low temperatures. Most modern chainsaws don’t require special adjustments if fresh, high-quality fuel is used.
• Eco-Friendly 50:1 Synthetic Oil Mixture: Synthetic oils reduce emissions and provide superior engine protection, making them a great choice for environmentally conscious users.

Storage Tips: Fresh is Always Better

Fuel quality can degrade over time, particularly gasoline that contains ethanol. To get the best performance, use fresh fuel and avoid storing mixed gas for more than 30 days unless you add a fuel stabilizer. Pre-mixed commercial fuels, however, can last up to 2 years unopened and a year once opened, making them a safer choice for occasional users.

Proper mixing and storage practices are essential to maintain fuel quality and ensure safe operation:

• Mixing Instructions: Use a clean, approved fuel canister (STIHL Canisters). Add the oil first, then the gasoline, and shake thoroughly to ensure a uniform mixture. For a 50:1 ratio, use 100ml of oil per 5 liters of gasoline. Avoid adding extra oil, as it can disrupt the balance and cause performance issues.
• Storage Guidelines: Mixed fuel should be used within 30 days to prevent separation and degradation, which can impair lubrication and cause engine damage. For longer storage, use ethanol-free fuel or add a fuel stabilizer to extend shelf life up to 12 months. Store fuel in a cool, dry place, away from direct sunlight and heat sources.
• Safety Precautions: Mix and refuel in a well-ventilated area, at least 3 meters from the work area, with the engine off. Avoid open flames, sparks, or smoking. Clean up spills immediately and change clothes if fuel contacts them to prevent fire hazards.

Key Points to Remember:

• Use the right gas-to-oil ratio (usually 50:1 or 40:1) as specified by your chainsaw’s manufacturer.
• Avoid ethanol-blended fuels when possible—opt for ethanol-free gas for smoother operation and less engine damage.
• Pre-mixed fuels offer convenience, longer shelf life, and cleaner burns, especially for casual or seasonal users.
• Always use high-quality two-cycle oil, ideally one recommended by your chainsaw brand.
• Don’t store fuel too long, and always keep it in a sealed, labeled, and approved container.

Common Mistakes and Troubleshooting

Using the wrong fuel mixture can lead to several issues. Here’s how to identify and address them:

• Excessive Smoke: Indicates too much oil in the mixture, which can cause carbon buildup and spark plug fouling. Recheck the ratio and remix with the correct proportions.
• Overheating: Suggests too little oil, leading to inadequate lubrication. This can cause engine seizure. Drain the tank, remix with the correct ratio, and check for engine damage.
• Loss of Power or Difficult Starting: Often caused by old or degraded fuel. Use fresh fuel and ensure it’s properly mixed. If the chainsaw doesn’t start, clean the spark plug and refill with the correct mixture.
• Stalling: May result from an incorrect mixture or contaminated fuel. Drain the tank, clean the fuel system, and use fresh, high-quality fuel.

If issues persist, consult your owner’s manual or a professional technician, such as a STIHL dealer (STIHL Dealers).

Conclusion

Selecting the best fuel for your chainsaw involves using a 50:1 mixture of high-quality unleaded gasoline (minimum 87 octane) and premium two-stroke oil, unless your model specifies otherwise. Ethanol-free gasoline is ideal for storage, while E10 is suitable for regular use. High-quality oils, like STIHL Ultra or Husqvarna premium mix, ensure optimal lubrication and performance. Proper mixing, storage, and safety practices are critical to maintaining your chainsaw’s efficiency and longevity.

Always refer to your chainsaw’s owner’s manual for specific recommendations, as requirements may vary by model and brand. By following these guidelines, you’ll keep your chainsaw in top condition for years of reliable service. Ultimately, the fuel you choose will impact how well your chainsaw performs and how long it lasts—so choose wisely.

Frequently Asked Questions

What petrol do I put in a chainsaw?

For most petrol chainsaws, you need to use a mix of unleaded petrol and two-stroke engine oil. The typical ratio is 50:1 (i.e., 50 parts petrol to 1 part two-stroke oil), but always check your chainsaw’s manual for the exact mix. Never use straight petrol, as it can damage the engine. Use fresh, high-quality unleaded petrol (usually 89 octane or higher) and a good-quality two-stroke oil designed for air-cooled engines.

Is it better to run premium gas in a chainsaw?

Using premium gas in a chainsaw isn’t usually necessary unless the manufacturer specifically recommends it. Most chainsaws are designed to run on regular unleaded gasoline with an octane rating of 89 or higher. Premium gas won’t harm the engine, but it generally doesn’t provide any performance benefits unless the chainsaw has a high-compression engine. More important than using premium fuel is ensuring you mix the fuel with high-quality two-stroke oil at the correct ratio and use fresh fuel to avoid engine problems.

Can I use motor oil for chainsaw petrol?

No, you should not use regular motor oil for mixing with petrol in a chainsaw. Chainsaws require two-stroke oil specifically designed for air-cooled engines. Motor oil, which is made for car engines, does not burn properly in two-stroke engines and can cause carbon buildup, poor performance, and engine damage. Always use high-quality two-stroke oil mixed at the correct ratio with petrol, as specified by your chainsaw’s manufacturer.

Should I run non-ethanol in my chainsaw?

Yes, running non-ethanol fuel in your chainsaw is generally better for engine health. Ethanol-blended fuels can attract moisture, which may lead to fuel separation, corrosion, and starting issues—especially if the fuel is stored for long periods. Non-ethanol fuel helps reduce these problems and extends the life of your chainsaw’s engine. While it may be more expensive or harder to find, non-ethanol fuel is a good choice if you want better performance and reliability, particularly for occasional or seasonal use.

What is a good substitute for chainsaw oil?

A good substitute for chainsaw bar and chain oil in an emergency is vegetable oil or canola oil. These oils are biodegradable, environmentally friendly, and have similar lubricating properties. However, they don’t offer the same tackiness and wear protection as proper chainsaw oil, so they may sling off the chain more easily and require more frequent application. Used motor oil should never be used, as it contains contaminants that can damage the chainsaw and harm the environment. Whenever possible, it’s best to use bar and chain oil specifically designed for chainsaws.

What if I put the wrong fuel in my chainsaw?

If you put the wrong fuel in your chainsaw—such as straight petrol instead of a petrol-oil mix—it can quickly damage the engine. Two-stroke chainsaws rely on the oil in the fuel mix to lubricate the engine. Running it on straight petrol, even briefly, can cause overheating, scoring of the piston, and possible engine seizure. If this happens, stop the chainsaw immediately, drain the incorrect fuel, and refill it with the proper fuel mix. If the chainsaw won’t start or runs poorly afterward, it’s best to have it inspected by a professional before further use.