Do Weed Wackers Need Oil?

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Owning a weed wacker means knowing how to use and maintain one properly. However, it is possible that your weed wacker may need oil, and you ought to know what to do when it does.

Maintenance Basics: Do Weed Wackers Need Oil?

It depends on what type of weed wacker you have. If you’re using electric or battery-powered models, then you don’t need oil at all, at least not in the usual sense. You may not need motor oil, but you may eventually have to apply some grease to the bearings to maintain the lubrication.

Now if you’re using a gasoline-powered motor, then you certainly need motor oil. Some of the latest commercial-grade models are now using four-stroke engines. These have separate compartments for your gasoline and for your oil. So, changing the oil is very similar to what you have to do when you own a car. Usually, the manual can indicate how often you need to change the oil to ensure that your weed wacker works properly.

Then there are the typical two-cycle engines. These use oil as well to ensure that the motor is properly lubricated. However, it’s not as simple as just changing the oil every now and then.

The Oil for 2-Stroke Engines

The main thing about these 2-stroke engines is that typically they don’t have a separate container for both the gasoline and the oil. Instead, there’s just a single container or reservoir. So, you have to add the oil to the engine, and that’s the mixture you pour into the fuel container. Eventually, the oil separates from the gasoline, and it lubricates the motor properly.

Gas Oil Ratio Mix for Weed Eater

You really won’t find “pre-mixed” gas and oil mixtures, so you have to mix the gasoline and oil together yourself. The ratio of oil gas isn’t uniform, as it depends on your particular model.

  • Most weed wacker manufacturers specify a 50:1 ratio. That means you need 2.6 ounces for every gallon of gasoline.
  • Other brands such as “Weed Eater” require a 40:1 ratio. That’s a mix of 3.2 ounces of oil for every gallon of gas.
  • Then there’s even the 32:1 ratio. This uses 4 ounces of motor oil for every gallon of gas.

Generally, you need the 2-cycle, air-cooled engine oil for your mixture. Fortunately, you don’t have to painstakingly measure out 2.6 or 3.2 ounces from your oil container to achieve your proper ratio for the mix. You can find the oil available in 2.6, 3.2, or 4-ounce containers. Just buy the right amount for your engine.

Why Does the Mix Have to Be Right?

You have to mix correctly with the right ratio to get optimal results. If you use too little oil, then the moving parts in your motor don’t get the lubrication they need. So, the friction can lead to a sudden lack of power, and then the engine will overheat. Eventually, you’ll have serious internal damage to the engine.

You may be tempted to use more oil than necessary to avoid overheating, but that’s an approach that can lead to its own set of problems. With too much oil, your machine may emit an excessive amount of exhaust smoke. In addition, you may also have problems with exhaust carbon buildup.

Do You Mix Straight Into the Weed Wacker Fuel Compartment?

NO! You have to get the mix right first, and then you can pour the mix afterward. To make sure you get the mix right, you need to buy the right amount of oil (and of course, a gallon of gasoline too). You should double check the manual to make sure of the oil container size you need.

  • Now you start the mix; you need a clean and empty gasoline can. Pour in all the oil from your container into the can. Now gradually ease in the gasoline into the mixture can. This mixture can have enough space to handle the addition of up to 4 ounces of oil.
  • Once you’ve emptied the gas can into the mix can, screw on the cap securely. Then shake and agitate the can to encourage the gas and oil to mix thoroughly.
  • Only mix enough gas and oil that you will use for the next 30 days. That’s because most gasoline products these days contain various additives that may break down the gasoline when you store it for the long term.

If you try to mix the gas and oil in the fuel tank of the weed wacker, then you’ll likely end up with a disaster. You probably won’t get the mix right since you may not be able to pour the entire one gallon of gas into the gas tank. Even if you somehow get the ratio right, you still won’t be able to blend the oil and gas properly.

Cleaning a String Trimmer Fuel Filter

String trimmers as you know are pretty easy to use and are very durable. However, to keep the trimmer running and performing at its best, proper maintenance has to be done along with understanding the right fuel and oil mixtures to use.

One of these important maintenance tasks is cleaning the fuel filter. By doing this, you can ensure that your trimmer runs well and starts as it should. To change the filter, you need to drain the gas from the trimmer. You then need to locate the rubber fuel line that runs into the gas tank and remove it. You will find the fuel filter of most models at the end of the line.

Once you remove the filter, you need to use a brush and mild soap to scrub it. Make sure to remove all excess water with a compressed air machine if possible. Finish drying off the filter with a clean cloth.

You can then replace the filter in the fuel line and fill the tank with fuel again and get back to trimming your grass and weeds. As with anything you do with your gas powered trimmer, it is always best to consult the manual beforehand to avoid any unnecessary damage.


There are always a lot of questions that arise when it comes time to put the oil in a weed wacker, so we have compiled a list of the more popular questions to provide you with a quick overview of what you can expect and what you may want to avoid.

Is it better to have too much oil or no oil?

While you want to avoid both of these scenarios, we would have to say that having too much oil is going to be slightly better than no oil at all. This is because no oil means fried pistons, smoke, and sluggish operation.

How do you know which oil or gas to use?

A two-cycle, air-cooled engine has one reservoir in which to put the gas and oil. The right combination of unleaded gasoline and oil needs to be mixed, but to do so; you need to refer to the user’s manual to be sure. Most require a 40 to 1 ratio in order to keep the engine lubricated. This ratio means that the trimmer requires 40 ounces of gasoline to one ounce of oil.

It needs to be fresh regular unleaded gasoline with no more than a 10 percent alcohol content. You should not use diesel fuel. Some warn against using automotive or boat engine oil for your weed eater, however, because of the formulation. It may not be right for the machine and can cause damage to the engine.

If you improperly mix the gas and oil, can it cause a leak?

Yes. If you do not get the mixture correct, it can cause engine damage, which can also lead to leaks and not enough lubrication.

Why do weed eaters need a gas and oil mixture to operate?

The trimmer’s engines require lubrication to continue operating at optimal levels.

What is the best fuel for lawn string trimmers?

The recommended fuel to use for lawn string trimmers is an 87-high octane gas with a maximum amount of 10% ethanol.

Related: Best Gas Weed Eater

How often should you change the oil?

It is important to change the oil out after 25 to 30 hours of usage. If this is the first time you are using your new weed wacker, you will want to do its first oil change after ten hours of use. Always make sure that the trimmer has clean oil.

What causes a weed trimmer to start smoking?

If your trimmer begins smoking, this could mean that you have the wrong fuel mixture, or it was improperly mixed. As soon as you see the smoke, turn the weed trimmer off, so you don’t accrue any additional engine damage. You will then want to drain the fuel and start over with the proper blend in order to keep the engine working properly. You also never want to use a fuel mixture that is over ninety days old because it can cause problems.

How do you know if there is too much or too little oil?

If you notice a blue smoke or oil begins dripping excessively from the string trimmer exhaust, you may have added too much oil. If you lose power as soon as the engine of the trimmer becomes hot, this could be a sign that you haven’t added enough oil. It may begin to overheat and give off an almost burning-like smell as well.


Does your weed maker need oil? If so, make sure you provide the right amount. Without lubricating oil, the engine can malfunction in just a few minutes, and you may even end up destroying the motor completely.

No matter what, you always want to use a high-quality oil. Check the manual for details because most manufacturers provide oil that was specifically tested for your particular weed wacker model. Because the trimmer runs at high speed and it creates heat and friction while it is in use, you want to be sure to find an oil with an American Petroleum Institute (API) designation.