Do Chainsaws Take Mixed Gas? Tips from a Professional


A two-stroke gasoline engine forms the backbone of various essential power tools such as a chainsaw. Gasoline chainsaws need to be topped up with fuel before they can be used. The fuel is usually mixed with engine oil in an adequate ratio. This blog post shall address some of the commonly asked queries regarding chainsaw fuel-oil mixture.

Do chainsaws take mixed gas?

Two-stroke engine chainsaws use gas mixed with suitable engine oil. The oil provides lubrication to the engine and for cooling. The ideal mixing ratio of gas to oil ranges from 40:1 to 50:1 for most chainsaws. A premix of 50:1 is prepared by mixing 2.5 oz of engine oil in 1 gallon of gasoline in a clean container. It is then added into the gas tank as per the need.

In this blog post, I will further explain how to deal with fuel mixes and show a step-by-step procedure for preparing it. I will also look at the ideal gas oil mixture for chainsaws and what happens when you use raw gas.

Do Chainsaws take Regular Gas?

Chainsaws use regular gas but are always mixed with suitable engine oil. Most gas chainsaws use a two-stroke engine that requires a mixture of gasoline and engine oil.

Chainsaw engines require a fuel premixed with engine lube to operate effectively. Running an engine on pure gasoline with no premix can overheat it and may damage components. The engine oil is needed to lubricate the moving parts of an engine and help to cool it down.

What Is the Gas to Oil Mixture Ratio for Chain Saws?

Most modern chainsaws require a fuel-oil mix of about 50:1. This means that 2.5 oz of engine oil should be mixed in 1 gallon of gasoline.

Unlike four-stroke engines, where the oil is inserted in the crankcase separately (they will have a separate engine oil compart), two-stroke engines require both fuel and oil to be mixed. The oil is needed to form a thin lubricant film to eliminate metal to metal to metal contact. Usually, the oil sits in between the narrow clearances meant for lubrication. If the oil in the premix is excess, it will burn alongside fuel in the engine, and you might see more smoke being released from the exhaust.

Fuel Mix: Our Recommendation for Ideal Mix

The correct gas-oil ratio will be mentioned in the owner’s manual of your chainsaw. The most common value prescribed is 50:1, meaning that 50 parts of gasoline mixed with 1 part of an oil or 2.5 oz of oil mixed in a gallon of gasoline.

For larger engines (greater than 75 CC), a lean mixing ratio is often recommended. This is done to support the lubrication for larger-sized components. For such engines, a 40:1 mixing ratio is ideal.

● Using a higher chainsaw fuel mix ratio:

If the mixing ratio is disturbed, that may affect the engine’s performance as it’s tuned to a different setting. A higher mixing ratio corresponds to a rich mixture (with more fuel content). This may be desirable if your priority is greater engine speed. In those cases, mixing ratios ranging from 60:1 to 100:1 can be used. I always recommend avoiding such ratios for engines larger than 75 CC.

Also, using a rich mixture in the long term can shorten your components’ service life. Always keep in mind that more fuel corresponds to higher engine temperatures.

● Using a lower fuel mix ratio:

A lower mixing ratio corresponds to a lean setting. This type of setting is suited for older engines (1960 models) whose pistons and cylinder walls are not strong enough to withstand high temperatures and speeds. Moreover, there is ample oil available for lubricating the components. Note that a too lean setting (such as 20:1) can reduce the engine’s power while cutting.

This is because excessive oil builds up around the spark plug electrodes, which diminishes the spark quality and disrupts firing. Thus, the power is significantly reduced. In this case, I recommend checking and cleaning your spark plug electrodes if the engine doesn’t provide sufficient power. Too much oil also creates deposits on the cylinder wall.

How to Mix Chainsaw Gas, Step-by-Step

Refer to the following procedure to create the fuel-oil mix for your chainsaw.

● Step 1: Select the suitable chainsaw oil type:

Before you begin, make sure you’ve chosen the correct type of oil for your chainsaw. The oil types are low smoke (LS) and high performance (HP) oils. Both of these oil types are synthetic.

  • High-performance (HP): High-performance lubes offer much cleaner burn in the engine and can work well with low-quality fuels. They are designed for use in small to medium-sized water-cooled engines.
  • Low Smoke (LS): Low smoke oils are instrumental in lowering smoke emissions from the exhaust. They also raise the components’ lifetime by keeping the engine’s overall temperature at a limit.

You can select any of the above types based on your priority. If a much efficient performance is desired, go with HP oils. While for reduced emissions, LS two-stroke oils should be preferred. While choosing the oil, another parameter to be considered is viscosity.

If you live in warm areas where the average temperature is above 70 degrees, always choose thicker oils such as 10W30 or 10W40. While in colder areas, go for thinner oils that will improve the engine’s cold starting, such as 5W30 grade lubricants.

I speak with many experienced chainsaw users, and most prefer high-quality two-stroke oil. Most choose lubes from brands like Stihl, Echo, Mobile 1, and Lawnboy. This is why I generally recommend using oil from such high-quality brands instead of some of the cheap alternatives

● Step 2: Choose the chainsaw fuel type:

After choosing the oil based on your application, select the proper gas type. The two most usual forms of fuel are ethanol-blended (E10) and standard unleaded. Both of these types are suitable for use in chainsaw engines. However, I would suggest that you should go for regular unleaded fuel that Is not blended with ethanol.

Such fuels enhance the performance and components’ life. Fuels blended with ethanol require increased maintenance of carburetor and fuel lines. Also, ensure that the octane number of the fuel is more than 89 to prevent wrong detonations.

● Step 2: Use a clean gas container:

The container storing the fuel-oil mixture should be clean. Dirty oil cans contaminate fuel by attracting dirt and debris. These deposits can accumulate and eventually jam the carburetor jets, making starting the engine difficult.

● Step 3: Prepare the Fuel-Oil Mix:

After choosing the suitable fuel-oil ratio for your device, prepare the mix as per the ratio. If your ratio is 40:1, you need to mix 3.2 oz of oil in 1 gallon of fuel. For a ratio of 50:1, mix almost 2.5 oz of engine oil in 1 gallon of fuel.

– Caution:

From my experience, I know that utilizing a crude oil mix (stored for 30 days) can negatively impact the chainsaw’s engine. Aside from stale oil, rich fuel/oil combinations (more than 50:1) are a major cause of engine seizures.

● Step 4: Add the Mix into the Engine:

Finally, the mixture is ready for insertion into your engine. Use a funnel to direct the mixture into the engine for more convenience. When the oil cap is full, seal it and mop up any spills that have occurred nearby. Your engine is now ready to go for a run. The container with the fuel-oil mix should be stored in a suitable space as it may be required again. If you intend to store it for longer than a month, I always recommend adding a fuel stabilizer. This prevents the fuel quality from degrading with time.

What Happens If I Put Raw Gas in a Chainsaw?

If raw gasoline is supplied to the engine without any lubricant, it would be detrimental to the engine’s components like the piston, cylinder walls, and crankshaft. This could result in the engine getting overheated and possibly scoring the cylinder walls or even causing a seizure.

The purpose of engine oil is to reduce metal-to-metal friction between moving parts. This eventually lowers the overall engine temperature and contributes towards a smooth and efficient performance. When the engine is deprived of the lubricant, the heat generated due to friction can affect it adversely. The drawbacks resulting are written below:

  • Cylinder walls scoring: When the temperature is high, and no lubricant is supplied to keep the pistons running smoothly, it is most likely to score the cylinder walls. This scoring of the walls reduces the engine’s compression. As a result, it won’t start or deliver lesser power when cutting.
  • Engine seizure: A more severe form of scoring is when the piston gets jammed in the cylinder, causing the engine to seizure permanently. The crankshaft doesn’t rotate, and the piston gets stuck. This happens if the engine is run without oil for a prolonged period. A complete engine replacement is the ultimate solution in this case which can be quite costly.

In most cases, running the engine on raw gasoline for 3-5 initial minutes doesn’t cause any apparent problem. If you’ve just realized after a few minutes that the gas is raw, turn the engine off. Remove all the gas in the tank and add a 50:1 premix to the gas tank. My experience is that if you turn the engine off quickly, there will not be any major issues.

If you want to be sure that it did not do any harm, you could check if the cylinder walls aren’t scored. You could do this by removing the exhaust and examining the cylinder walls. A lot of chainsaw users who’ve run their saws for over 30 minutes with gas without oil end up ruining their engines permanently.

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