What 2-Stroke Mix Ratio Does a String Trimmer Use?

String trimmers are used in short bursts a few times a month, which means the same tank of premix often sits for six to eight weeks. That is well past the point where untreated two-stroke mix starts to go off, and it is why trimmers are the tool most often brought in with a gummed carburettor.

Mix small batches, use a stabiliser if the can will sit, and pour off anything older than about a month rather than running it. A trimmer carburettor is small enough that a little varnish blocks it completely.

Stihl, Husqvarna, Echo, Shindaiwa and Makita trimmers are 50:1 across their current ranges. Budget and older tools are where it varies: some Ryobi, Homelite, Troy-Bilt and Poulan models call for 40:1 or 32:1, and a few older units were sold with the maker's own oil at a specific rate.

Check the fuel cap decal first. If the tool has an attachment-capable powerhead shared across a brand's line, the ratio belongs to the powerhead, not the attachment, so the same mix runs the edger, pole saw and brush cutter heads.

• Hard starting after a few weeks idle, then running only with the choke half on, is almost always stale fuel rather than the mix ratio.
• Heavy smoke plus a wet plug right after mixing a fresh can means too much oil, usually a full 2.6 oz bottle dropped into less than a gallon of gas.
• Loss of power under load with a clean plug is often a clogged spark-arrestor screen, which a rich mix accelerates. It unscrews from the muffler and cleans with a wire brush.
• A trimmer that revs but will not hold high rpm can be a fuel line or filter perished by ethanol rather than anything to do with the oil.