Weed eaters, weed wackers, trimmers; whatever you call them, are immensely useful garden tools that help you to cut through brush, weeds, and long grass. There are many electric weed eaters on the market but those that are powered by gas are typically much more efficient and able to deal with more challenging conditions.
However, since there are several moving parts within the fuel system and engine of your weed eater, it’s essential that these are lubricated. This is done using engine oil but the type that you need will depend on the type of engine your weed eater runs on.
Gas weed wackers either have a two cycle or a four cycle engine. What this means is how many times the pistons inside the engine move up and down to complete one fuel cycle. Each type of engine requires a different type of oil and it’s vital that you only use oil designed specifically for your engine type. If you don’t, then there is a risk of problems that could be difficult to fix.
Four cycle weed eaters have separate compartments for the oil and the fuel while two cycle machines require the user to create a mix of fuel and oil that is then deposited into the fuel tank. In this guide, we will look at the right oil for weed eaters and how you should use it.
Two cycle, sometimes called two stroke weed eaters, take a blend of fuel and oil which is put into the same tank. If you do not do this, and simply add only fuel then there will not be sufficient lubrication within the engine and the parts will not be able to move freely.
Don’t ever be tempted to skip the oil as this will cause major problems. In fact, when using straight fuel in a two cycle string trimmer, you’ll likely end up seizing the engine which could stop working altogether.
There are different ratios required depending on your string trimmer and the best place to find the correct information for this is in your user manual. However, generally speaking, weed eater oil will be mixed with the following ratios:
- 50:1
- 40:1
- 32:1
This means that, if your engine requires a 50:1 mix, you will need to mix 50 parts fuel to 1 part oil. If you can’t find the information in your user manual or you have misplaced it then the correct ratio is also usually found on a label on the fuel cap.
When creating a fuel and oil mix for your gas powered string trimmer, you will need to ensure that you use unleaded gasoline. Moreover, your gas should have an octane rating that is no lower than 89; these are mid-grade fuels. On top of this, you should also be looking for fuel whose ethanol content does not exceed 10%. There are fuels out there with even lower ethanol contents than this so if you can get your hands on those, then that’s even better.
When buying oil for 2 cycle weed eater engines, you will need to select a product that has been specifically designed for this purpose. The bottle will be labelled as a 2 cycle premium oil. You should also check that your chosen oil is also JASO M345 FD and ISO L EGD certified.
2 Cycle Gas And Oil Mix Ratio
As we have discussed, you will need to find out the correct fuel and oil ratio for your particular machine. Never guess this as you’ll likely get it wrong and end up damaging your weed eater. If you can’t find the information in your user manual or on the fuel cap then you’ll be able to look up a digital user guide by searching your make and model online.
But once you know the right ratio and how much fuel your tank can hold, you’ll be able to figure out how much oil you need to put into the mix. Here’s a table to make it simpler.
| Ratio | 50:1 | 40:1 | 32:1 |
| 1 Gallon Tank | 2.6 oz | 3.2 oz | 4.0 oz |
| 2 Gallon Tank | 5..2 oz | 6.4 oz | 8.0 oz |
| 3 Gallon Tank | 4.0 oz | 8.0 oz | 10.0 oz |
The Oil For A 4 Cycle Weed Eater
Some string trimmers run on a four cycle engine and these are different from two cycle engines in that there is a separate port for oil and another one for the fuel. In these machines, it is vital that you never blend the gas and oil together. Moreover, you will need to choose an oil that’s appropriate for your engine; 2 cycle oils are not to be used.
Again, with a four cycle engine, the oil is required to lubricate the internal parts and keep them moving. If the incorrect type of oil is used then this will cause friction which can, in turn, make your engine overheat. As a direct result of this, you’ll find that the string trimmer won’t start up.
One thing that you need to keep in mind when choosing oil for 4 cycle weed eater engines is the viscosity. This is because different oil viscosities will be more suitable for varying temperatures. For example, you’d need something different for use in hot climates than you would in a colder climate.
4 Cycle Gas And Oil Ratio Mix
When it comes to using oil in a four cycle weed eater engine, you don’t need to worry about ratios. This is because the oil and fuel won’t be mixed together. However, you will need to think about the viscosity, as I mentioned before and this will depend on the type of machine you are using.
As before, you will be able to find details of the most appropriate engine oil in your user manual. If you cannot find this, searching for the make and model online will yield the results you are looking for.
However, as a general rule, the following manufacturers recommend the following types of oil.
| Weed Eater Brand | Best Engine Oil |
|---|---|
| Troy Bilt | SAE 30 |
| Ryobi | 20W 50 |
| Powersmart | SAE 30 |
| Makita | 10W 30 |
| Husqvarna | 10W 40 |
| Honda | 10W 30 |
| Craftsman | SAE 30 |
How To Mix Gas And Oil For A Weed Eater
The table in the previous two cycle section above will allow you to easily find out how much oil you need to use per gallon of fuel. When you have figured this out, you will need to mix the liquids before putting them into the fuel tank.
You must use an approved gas can and when you’re ready, take off the cap and put in your unleaded fuel. Remember that this should have no more than 19% ethanol and be no lower than 89 octane.
When choosing a gas can, try to find one that is a similar size to the amount of fuel you’ll be mixing as this often makes it easier. You’ll use this can over and over again so it’s wise to mark it with something like two cycle fuel and oil mix so that it doesn’t get confused with anything else.
You’ll already be aware of how much oil you need to add and now it’s time to put it into the fuel you just added. When you have done this, replace the fuel cap and gently shake the can so that the oil and gas can combine.
You’re now ready to add the mix to your weed eater and get on with those garden chores. However, you should keep an eye out for anything suspicious which could be an indicator that you have incorrectly mixed the fuel and oil.
Things like smoke coming out of the engine or a lot of heat could signal that the mix is wrong. This can also happen if you use an old mix so always try to use something fresh. If the mix is any more than 90 days old then it’ll likely cause problems.
If you do notice any problems then make sure to turn your weed eater off immediately otherwise you risk damaging the engine. Now drain away any leftover fuel mix and try again with a new batch.
Final Thoughts
Depending on whether you have a two cycle or a four cycle weed eater, you will need to use different types of oil. Not only this but the way that you put the weed eater oil into your machine will differ. Two cycle engines require the fuel and oil to be mixed together while four stroke engines have two tanks; one for oil and one for fuel.
It’s important that, when mixing gas and oil, you get the correct ratio. Moreover, you should always ensure to use a high quality oil as well as appropriate fuel so that your weed eater runs without any problems.
