Chainsaws need fuel to run. Without fuel, our chainsaws are just useless pieces of metal and plastic. Chainsaws (not including electric or battery units – which are actually a thing now) are powered by a 2 stroke engine that requires fuel mixed with a proper ratio of oil. If straight gasoline is run in a chainsaw it will likely result in catastrophic engine failure. Do not make this mistake. Make sure to mix your oil properly so that your chainsaw functions properly for years to come.
Mixing fuel for a chainsaw is done by combining the appropriate amount of 2-Cycle oil and Gasoline together in the proper ratio laid out in the owner’s manual for your particular chainsaw.
Different chainsaw manufacturers require different fuel ratio mixtures. Running the incorrect mixture can cause the chainsaw to either run too rich or too lean. Running rich means the fuel contains too much oil and can cause the unit to smoke, foul the spark plug or clog the muffler. Running lean means the fuel does not have enough oil and can result in the damaging of the engine by scaring the piston, cylinder, and rings.
Stihl, Husqvarna, Dolmar, Maruyama, and Echo typically require a fuel ratio mixture of 50:1 Poulan typically requires a fuel ratio mixture of 40:1 Please keep in mind that this is a general rule of thumb. Always consult your operator’s manual to be sure you have the exact fuel ratio mixture for your chainsaw.
Once you have determined the correct fuel ratio mixture you need to purchase the correct amount of oil for your chainsaw. You need to be sure to read the label for the volume of oil and the mixing ratio.
Refer to the chart below to make sure you’re using the correct 2-cycle fuel and oil mixture:
| Mixing Ratio (Gas: Oil) | Volume of Gasoline | Volume of 2-Cycle Oil |
| 32:1 | 1.0 US gal. (128 oz) | 4.0 oz. |
| 40:1 | 1.0 US gal. (128 oz) | 3.2 oz. |
| 50:1 | 1.0 US gal. (128 oz) | 2.6 oz. |
| 32:1 | 1.0 Liter | 31.25 ml |
| 40:1 | 1.0 Liter | 25.0 ml |
| 50:1 | 1.0 Liter | 20 ml |
When it comes to the actual mixing of the fuel and oil; simply pour the contents of the oil bottle into the appropriate amount of fuel and shake well. That’s it. You’re ready to cut some wood.
There are 2 more issues that need to be addressed with respect to fuel that most people do not realize.
The first of which is the age of the fuel in your gas can. Most people will mix fuel and let it sit in the garage for months. This is a formula for having a chainsaw that won’t run at all or at least won’t run correctly. Think of gasoline as you think of the milk in your refrigerator. You wouldn’t drink 3-month-old milk, would you? I didn’t think so. So why use 3-month-old fuel in your chainsaw? Gasoline expires the same as milk.
If gasoline is more than a month old, DO NOT USE IT in your chainsaw.
The second issue is the ethanol content in your fuel. What is ethanol you ask?
Ethanol, also known as ethyl alcohol is used as a biofuel additive in most of the fuel today. As a general rule of thumb, ethanol of up to 10% is generally ok for use in small engines like those that power chainsaws. Notice I said generally ok and not absolutely ok. Fuel with up to 10% ethanol will run fine but will cause issues with your chainsaw over time. These issues include the hardening and cracking of rubber and plastic materials like fuel lines, grommets, and seals. There is another grade of ethanol fuel known as flex-fuel that contains up to 85% ethanol.
Do not run flex fuel in your chainsaw. It will seriously damage or destroy the unit. Never run fuel with more than 10% ethanol in your chainsaw. At least not in the chainsaws we have today. I’m sure there are chainsaws being engineered that will be able to handle flex fuels just fine. However, they are not currently on the market for sale.
It is best to run ethanol-free gasoline, (if you can find it), with a high octane rating in your chainsaw. The higher octane-rated gasoline helps to combat things like pre-detonation within the engine.
What is the correct fuel mix for chainsaw?
The correct ratio of 2 cycle oil mix for chainsaws varies from brand to brand and must be strictly adhered to as to avoid damaging the chainsaws 2-cycle engine. What is the correct fuel mixture for your chainsaw?
Refer to the chart below to determine the proper oil mixture for your chainsaw.
| Brand | Ratio | Ounces/Gallon |
| Stihl | 50:1 | 2.6 oz |
| Husquvarna *certain applications with engines above 75cc can be run on a mixture of 33:1 | 50:1* | 2.6 oz |
| Echo | 50:1 | 2.6 oz |
| Jonsered | 50:1 | 2.6 oz |
| Poulan | 40:1 | 3.2 oz |
Check with your chainsaws operator manual to verify the following information is still accurate as manufacturers update oil mix requirements from time to time
How much 2-cycle oil do you put in a gallon of gas for a chainsaw?
The correct amount of oil must be used to get the ratio of oil and gasoline correct in a 1-gallon fuel can. What is the correct amount of 2-cycle oil for 1 gallon of gasoline?
A chainsaw fuel mixture of 50:1 requires 2.6 oz of 2-cycle oil to be mixed in 1 gallon of gasoline. A mixture of 40:1 requires 3.2 oz of 2-cycle oil to be mixed with 1 gallon of gasoline.
Wrapping Up
Chainsaw’s 2 cycle engines are made with very tight specifications and run at very high RPMs that require properly mixed and fresh fuel. Always make sure that your gasoline is properly mixed with the correct ratio of oil for your particular brand and model of chainsaw. Remember that the wrong mix can destroy your chainsaw. Also, never use gasoline that has been sitting around for more than 1 month. Old fuel causes problems and it is best to just avoid it.
Have a great day and be safe.
Always be sure to only use EPA-approved fuel containers along with hand and eye protection.