Which Kind of Fuel is Best for Lawn String Trimmers? PM Lab Test

• trimmers
• gardening
• lawn care
• string trimmers
• propane
• batteries

When it comes time to trim the lawn, a mower will only get you so far. For the finishing touches, you have to rely on a string trimmer, known in backyard vernacular as the weed whacker. At the moment, there are a number of different styles and brands on the market, each offering different capabilities. I recently had the opportunity to check out three new trimmers—two of which had cutting-edge fuel types—to see how they rated against one another.

I tested the Worx GT Cordless Trimmer ($150), powered by an 18-volt lithium-ion battery; the four-cycle Lehr Propane Trimmer ($180), powered by a small 25-cc propane tank; and Troy-Bilt's two-cycle TB80 EC, which launches in the next few months and runs on the traditional gas/oil mix. I set up a specific test to rate the power and stamina of the machines, but I also used each one around the yard under normal circumstances to get a general feel for ergonomics, noise, and ease of startup.

Raw Power

To investigate the strength of these trimmers, I trekked a quarter-mile behind my house to an abandoned quarry and found an area filled with waist-high weeds, overgrown crab grass, and a host of other unwanted, sinister-looking plants. It reminded me of the terrain that Frodo and Sam traveled on their way to Mordor. For the test, I staked out three identical three-foot by 3-foot squares, and recorded the time it took for each trimmer to reduce its designated area to a putting-green level of growth.

First up was the Craftsman-branded Lehr four-cycle propane trimmer. This one cleared the area in a hasty eleven seconds. The trimmer was very aggressive and went through the thicker weeds without pause. When I was done, it looked as if the area had been prepped for a helicopter landing.

The Troy-Bilt two-cycle gas/oil was next. It accomplished the task one second faster than the Lehr, clocking in at ten seconds. Once again, total weed devastation.

Up last was the Worx 18-volt battery trimmer. Just looking at the light-duty tool, I knew it was out-matched by the tangled mess of growth, but I fired it up and had at it. The Worx put up a much better fight than I thought it would. In 30 seconds, it managed to cut all but the thickest weeds.

Winner: Troy-Bilt

Run Time on a Full Tank

To test the run time of the Worx, I clicked in a freshly charged battery, duct taped the trigger down on full throttle and started the stopwatch. Because the trimmer is so quiet, it was no problem running the test until the battery died, which occurred at some point during the 26th minute.

I then taped up the Troy-Bilt trimmer and started the timer. This testing took place in a residential neighborhood at twilight, and it wasn't long before I got a little wary about how long the experiment would last with the intense screaming of the fully engaged two-stroke engine. So I called it quits at about 20 minutes. But I recorded the gas/oil tank level at the start of the test, and what remained led me to believe that the fuel would last well over an hour running at constant maximum speed.

Lehr's manufacturer claims a run time of about 2 hours (the opaque tank prohibits a visual check, and noise again limited the test length). Even if the Lehr didn't last the complete two hours at full throttle, it's safe to say that both the propane Lehr and the gas/oil Troy-Bilt can squeeze a single tank of fuel for at least twice as long as the battery-powered Worx.

Winner: Troy-Bilt and Lehr

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