Everyone who owns a chainsaw knows that frequent maintenance is essential. Usually this involves things like making sure your chainsaw is clean, that it has a proper lubrication, and that it’s running on the right type of fuel.
But chainsaws are not like a regular car or motorcycle with a 4-stroke engine – they need a mixture of gas and oil to run.
But do all chainsaws take mixed gas? Yes. All gas-powered chainsaws need gas mixed with oil in order to work correctly. The mixed gas ensures the smooth operation of the engine by providing lubrication and reducing its temperature to manageable levels. This is achieved by mixing oil and gas in specific ratios.
Although all gas chainsaws need mixed fuel, there are some important caveats to that.
Read on, as I explore what makes the chainsaw’s engine different and what you need to know about mixing the gas.
Which Chainsaws Take Mixed Gas?
Mixed gas refers to combining the gas that some chainsaws use with oil. There are specific ratios that need to be followed when doing it, and we will get to that in a bit. But first, we need to make a few important distinctions.
Let’s start by first establishing the different types of chainsaws that we can use. There’s a few of them:
- Gas (or petrol) operated chainsaws;
- Electric chainsaws; and
- Battery (or cordless) chainsaws;
I am sure that you are suspecting not all of these need mixed gas. In fact, only the gas-operated chainsaws take mixed gas, because they are the only ones actually running on gas.
Both the electric and battery-powered chainsaws use electricity as their power source. They don’t need gas, and consequently, don’t need oil for their motor.
However, let me point out quickly that every type of chainsaw, regardless of how it is powered, does need oil for the lubrication of its chain. New chainsaw owners often get confused by this, so I’ve written an article about this very topic, you can check it out here.
How Does the Type of Engine Affect the Fuel Mixture?
Using a 2-Stroke Chainsaw
A lot of us have experience with four-stroke engines, as they are frequently used in cars, motorbikes, and more. They usually don’t need any mixed gas, but chainsaws are different.
The majority of chainsaws use a 2-stroke engine that doesn’t have a separate oil lubrication system; as a result, it needs the oil to be manually added to the gas.
Failing to do so, you are risking destroying the engine of your chainsaw.
Using a 4-Stroke (?) Chainsaw
The vast majority of the chainsaws have two-stroke engines. However, there are some models like the Stihl 4-MIX, which do have a four-stroke engine.
This is a kind of hybrid engine developed by Stihl that runs pretty much like a regular 4-stroke engine, but unfortunately it still runs on mixed gas. In short, you’ll need mixed gas no matter what chainsaw you buy.
There many reasons to the absence of real 4-stroke chainsaws – I wrote an article on this very topic, you can go check it out here if you are interested.
What Is the Right Oil to Gas Ratio for Your Chainsaw?
The best way to ensure your chainsaw will be working for the many years to come is by properly mixing your fuel.
The right oil to gas mixture ratios may vary significantly depending on the chainsaw. For example:
- Some older chainsaw models use 30:1 mixture;
- Many of the modern chainsaws may need 40:1; and
- Some chainsaws, including some Stihl models, may need 50:1.
But what does that really mean?
- A 40:1 ratio will translate into 3,2 ounces of oil for every gallon of gasoline; And
- A 50:1 would mean you need to add 2,6 ounces of oil per gallon of fuel.
Seeing how the right ratios can vary, the best thing to do is to always check your user’s manual, as manufacturers should clearly state what the correct fuel mixture for your particular model is.
A very helpful thing to know is that you can also buy premixed fuel, which takes all the math out of the way. These are usually more expensive than mixing your fuel yourself, but they are a good choice if you aren’t sure what you are doing, or for when you are in a hurry.
The rule of thumb is that generally speaking, it is much better to have a little too much oil than not enough. Running your engine with slightly more oil may lead to some smoke and more exhaust fumes, but the oil will still protect your engine.
What Are the Right Fuel and Oil Type?
The fuel mixture can be only as good as its components. And chainsaws can be considered a bit picky in that regard.
So let’s take a look at what you need to know in order to have your chainsaw running smoothly:
The Octane Rating
The majority of chainsaws require fuel with a minimum octane rating of 89 or higher. Usually, there isn’t much benefit of going higher than 91 octane unless your chainsaw has been modified in specific ways.
Going with lower octane rating, although cheaper, is actually not recommended. Lower octane fuel will not only severely cap the performance of your chainsaw, but it can also damage your engine.
This is because of the difference of peak pressure in the cylinder is going to be slightly different with lower octane rating fuels which can ultimately damage the entire engine.
The Ethanol Percentage
A thing that frequently gets overlooked is that gas today contains ethanol. And ethanol can be quite damaging to our little chainsaw’s engine.
The E number indicates the amount of ethanol in your fuel. So an E10 would mean 90% gas and 10% ethanol. Some of the more common are E10 and E15, and there is even E85.
Unfortunately, not a lot of user manuals talk about this, but the only one you can use is the E10. And even this is not the best way to go.
The best fuel for your chainsaw is ethanol-free gas.
Using the right type of oil is going to ensure that your engine is running smoothly and is adequately lubricated.
Make sure to use proper two-cycle motor oil.
This is a type of oil that is designed specifically for two-stroke engines. It is not as heavy as four-cycle motor oil, but it burns more efficiently.
What Happens If You Don’t Mix the Gas with Oil?
Although the chainsaws we have today are a lot more efficient than their distant and old relatives from several years ago, one thing remains unchanged; they all require mixed gas.
And there are a few reasons for that:
- The oil lubricates the piston, keeping it running smoothly;
- The oil lubricates the crankshaft, making sure it works optimally; and
- The oil keeps the engine running at lower temperatures.
The dangers associated with running on pure gas (which is not mixed with oil) are:
The Engine Will Run on Higher Temperatures
The pistons inside the engine move with high speeds, which creates a lot of friction. The same thing applies to the crankshaft. All this friction produced by the piston and the crankshaft generates tremendous amounts of heat.
The oil that is mixed with the fuel adds much-welcomed lubrication, which lowers the temperature at which the engine runs.
A word of caution: running your engine without mixed gas is not recommended, as it will ruin your chainsaw in a matter of minutes. Always make sure to follow the recommended maintenance procedures noted in your user’s manual that arrived with your chainsaw. Failing to do so may lead to a warranty void by the manufacturer.
Potential Piston and Engine Failure
The high heat resulting from the lack of oil and lubrication can eventually cause the metal from which the piston is made to expand.
When this happens, the piston will not be moving as smoothly as it should be, and it will start damaging the engine itself.
It doesn’t take more than a few minutes for the damage to happen and the engine to stall.
Usually when something like this happens, the end result is a completely ruined engine that is unusable.
Unfortunately, in most cases there is nothing that can be done in order to fix the engine.
The cost of buying a new machine is almost always going to be significantly less compared to fixing and replacing the broken parts of the engine.
Can You Add Oil in the Fuel Tank Later?
You may wonder what happens if you accidentally forgot to mix the oil with the gas, and you have added raw gas in the fuel tank of the chainsaw.
First, let me start by saying that you shouldn’t worry. Just make sure you do not start the chainsaw.
What you need to do now is just drain the gas from the tank. Experts also recommend to add one tsp. of water into the tank, shake it a bit and pour it out. Then it is recommended to change the fuel lines and remove the carburetor if you can, and clean it.
After that, proceed with adding the mixed fuel.
Resources and further information:
- Husqvarna.com – What is ethanol fuel and why is it bad for your small engine outdoor power equipment?