Do String Trimmers Need Oil?

Last Updated on June 5, 2024 by Duncan

String trimmers, often known as weed trimmers, come in handy when it comes to maintaining your outside areas.

A properly maintained trimmer may readily cut weeds and grass as needed, as well as edge paths, for a tidy appearance.

If you are new to string trimmers, you might be wondering whether they need oil, right?

Well, yes, they do.

2 stroke string trimmer

If you have a two-stroke strimmer, you need to add oil to the gas. Unlike engines with separate gas and oil reservoirs, 2 stroke engines run on a combination which keeps the engine constantly lubricated.

You should never put plain gas in a two-cycle engine since it will destroy it in minutes.

For the best outcome, use the proper fuel combination when operating your lawn trimmer or brush cutter.

You should note that unsuitable fuels and incorrect mix ratios can cause major damage, including piston seizure, excessive wear, and, ultimately, a shorter life for your grass trimmer. And you don’t want this, do you?

When preparing 2-stroke gasoline for your trimmer, consider the following mix ratio:

1:50 = 1-part oil + 50 parts petrol

Make your grass trimmer fuel mixture in a receptacle certified for use with fuels. You should pour in the oil first, then the petrol; seal the canister, and shake vigorously to blend the fuel mixture.

By doing this, you are ready to use the gasoline mixture in your lawn trimmer or brush cutter tank. Take care when opening the canister, as pressure may have built up within.

4-stroke string trimmer

If you have a string trimmer with a 4-cycle engine, you still need oil in your engine, but you do not need to blend the fuel and oil like you would with a 2-cycle engine.

While this is the case, you should check the oil level before each use. The importance of this step cannot be overstated. It is critical to have the correct level of oil in your equipment. In order to accomplish this:

Make sure the engine is turned off and cool to the touch.

Place the string trimmer on a flat, level surface, like a workbench or table. The cutting head should hang over the edge, ensuring that the engine is level.

Check the oil level. The method for checking the oil level varies depending on the model. Some variants include a dipstick linked to the oil fill plug while some models include an oil-level window.

If the oil level is too low, apply more oil to reach the proper level. Don’t overfill the reservoir.

Most manufacturers recommend changing the oil after the first 10 hours of operation, and then every 28 hours afterward. To change the oil:

Make sure the engine is turned off. However, change the oil while the engine is still warm. This allows the oil to flow freely and removes more of the contaminants that have accumulated over time.

Clean the area surrounding the oil fill cap to keep debris from entering the oil fill hole.

Unscrew the oil filler plug.

Tip the unit vertically to pour the oil from the oil fill hole into a container. Allow enough time for thorough draining.

Clean up any oil that may have leaked.

Pour fresh oil into the oil fill hole.

Clean up any oil that may have leaked.

Re-install the oil fill plug.

Once you are done, dispose of old oil in accordance with federal, state, and local requirements.

Other ways to ensure your string trimmer is in top working shape

Besides ensuring that your trimmer has the right oil in the engine, there are plenty of other things you need to do to ensure that your trimmer is always in good working condition. These things include:

Inspect the air filter

Cleaning and re-oiling the string trimmer air filter is a must. A clean air filter boosts performance and protects the engine. To clean the air filter:

• Make sure the engine is turned off and cool to the touch.
• Open the filter cover and take out the air filter.
• Replace the filter if necessary. If you’re reusing an existing air filter, wash it with detergent and water. Rinse the filter and allow it to dry.
• To prevent junk from being drawn into the engine, lightly coat the filter with clean SAE 30 oil.
• Squeeze the air filter to disperse the oil and eliminate any excess.
• Reinstall the filter in the trimmer and seal the cover.

Inspect and install the spark plug

You should replace the string trimmer spark plug on a regular basis.

• Make sure the engine is turned off and cool to the touch.
• Remove the spark plug boot.
• Use a 5/8 socket to remove the spark plug. Examine the spark plug to determine if it is fouled, blackened, rusted, or damaged.
• If necessary, replace the spark plug with the kind recommended for your trimmer. You can find this information in your owner’s manual.
• To set the gap, use a feeler gauge and follow the instructions in your manual.
• Reinstall the spark plug and tighten it using the 5/8 socket clockwise until snug. Don’t over-tighten the spark plug.
• Place the spark plug boot back on the spark plug.

Replace the trimming line.

You should replace the string trimmer’s trimming line numerous times per season as it wears out, therefore it’s almost certain that you will require a new line before running for the first time each year.

Even if you put a new line on it shortly before storing it for the winter, the material is likely brittle and will not cut much before requiring replacement.

Each model is slightly different, so follow the manufacturer’s recommendations. To replace the line:

• Hold the inner reel while unscrewing a knob in the center of the trimmer head to separate it from the outer spool.
• Attach a pre-wound inner reel or manually wind a string around the interior of the reel. This is accomplished by either looping the center of the line around a slot in the reel or feeding it through holes at the top and bottom of the reel.
• Once you are done, replace the reel and thread the line ends through the head’s holes.

Keep the string trimmer clean.

Leaving dirt, grease, or chunks of chopped grass on the trimmer will only cause rust and other problems over time. So, you will need to clean it.

If you have an electric trimmer, besides cleaning it, you need to inspect the battery or cord for signs of damage. Batteries that are swollen, damaged, or discolored should be changed and thrown.

If the string trimmer’s cord is cut or damaged, you will need professional engine repair before you can use it again.

Parting shot

As you have seen, you need to oil your 2 stroke or four-stroke string trimmer.

When it comes to maintenance, string trimmers can easily last for years without needing to be serviced, but don’t be fooled. You could end up with a trimmer that won’t start when you need it most.

Taking care of this piece of lawn equipment on an annual basis is a far better way to ensure that it’s in top working shape at all times.