What Kind Of Oil Do Weed Eaters Need And How Often Should You Change It?

With the change in seasons comes the unrelenting need for more yard work, as Mother Nature does her best to keep us on our toes. For those of us who have yards to tend to, weeds sprout up each year like clockwork, making nicely trimmed grass look disorderly. That's when you reach for your weed eater or weed whacker, a trusty handheld tool that allows for the neat cutting of wild grass and weeds, usually available in gas-powered or electric versions. 

There are a ton of grass trimmer brands on the market. With gas weed eaters, keeping the motor humming along nicely is key to keeping pesky weeds at bay all summer long. However, running for hours on end under the hot sun can be taxing on these machines, where keeping them in tip-top shape is key. Choosing the right oil to lubricate a weed whacker engine is tied to its design and type, and must be understood to avoid issues.

With 2-stroke or 4-stroke engines powering many weed eaters, each type requires its own maintenance style to ensure performance and reliability. Users must first know which type of motor powers their machine, in addition to consulting the manual, for insights into oil requirements. If no manual is available, engine damage can be avoided with some careful research and expert advice. Here, we will help navigate weed eater oil requirements to help you avoid a catastrophe similar to running a car engine without oil and keep your property weed-free all summer long.

Understanding the differences between 2-stroke and 4-stroke engines may help users understand more about the care and oil requirements. In a 2-stroke engine, the moving parts are lubricated by oil mixing with the gasoline, which gets used up during combustion. As such, the oil lubricates all of the moving parts inside the engine during operation, where these systems don't have a separate oil reservoir. 

Alternatively, a 4-stroke weed whacker has a dedicated oil sump, similar to a car engine, where oil is kept on reserve and circulates through the motor while under power, keeping moving parts lubricated. The oil in a 4-stroke is not burned during operation, unlike that of a 2-stroke. Look for oils that meet or exceed JASO FD standards, which will burn cleaner, lube better, and smoke less.

2-stroke weed eaters need oil that is formulated for air-cooled engines, which is usually designated as "TC" or with "API TC +" descriptors. A 50:1 ratio is the most common for these motors, with 50 parts of gas to 1 part oil. However, some engines may require different ratios like 40:1 or 32:1 — as such, checking the user manual is recommended. 4-strokes require oils of differing viscosities, depending on the temperature range they are operated at. SAE-30, 10W-30, AND 5W-30 are common formulations, with SAE-30 being optimal for hot summer days, 10W-30 working across a wider range, and 5W-30 working best in the cold.

Much like a car or motorcycle, weed whackers require regular oil changes to keep those pistons happy. The one caveat here is that 2-stroke motors offer the advantage of not requiring oil changes in the normal context due to their design, which simplifies operation. However, it places more emphasis on making sure the fuel-to-oil ratios are adhered to and mixed, lest you prematurely wear out the internal components.

For those users out there with brand-new 4-stroke weed eaters, there is a "break-in" period to consider, which comprises the initial 10 hours of operation. It is critical to change the oil after this breaking-in period to remove contaminants that accumulate in the oil, potentially damaging internals if left unchanged. 

Checking the level of oil before proceeding to tackle those pesky weeds will inform users when to top up. Some manufacturers like Honda and Craftsman recommend changing a 4-cycle motor's oil every 38 to 50 hours of operation, either by a qualified service dealer, or a savvy user. Changing the oil is recommended each season at a minimum, to start off on the best foot. Additionally, if stored for long periods of time in a shed, adding some fuel stabilizer will help to prevent gas from getting gummy, protecting the unit. The bottom line is that a gas-powered weed eater requires the right oil at the right time — but it doesn't have to be complicated.