How to Mix Chainsaw Gas | A 50:1 Fuel Recipe That Runs Clean

Getting the fuel mix wrong is the fastest way to shorten a chainsaw’s life, yet the recipe trips up plenty of owners. The short version: most modern chainsaws run on a 50:1 ratio, which means 2.6 fluid ounces of 2-stroke oil per gallon of fresh gasoline. The longer version matters more. Your saw’s exact ratio depends on the brand and the oil you use, and the number stamped on the bar tells you nothing. The owner’s manual is the only source that settles it, but the steps for mixing are the same across brands.

What Ratio Does Your Chainsaw Need?

STIHL USA states that most STIHL gasoline-powered equipment runs on a 50:1 mixture of gasoline and 2-cycle engine oil. Husqvarna’s US support recommends 50:1 (2%) when using original Husqvarna 2-stroke oil, but that shifts to 33:1 (3%) if you use another brand of 2-stroke oil. The reason is oil formulation—brand-specific oils carry additives that let them lubricate at leaner ratios.

The takeaway: check the manual before you pour.

The Mixing Steps That Work Every Time

These steps follow the method STIHL and Husqvarna both document, and they keep the oil from pooling in the can:

1. Use fresh unleaded gasoline with an octane rating of 89 or higher, and the 2-stroke oil your saw’s manual specifies. For non-brand oil, Husqvarna’s manual calls for a quality oil made for air-cooled engines.
2. Pour about half the gasoline into a clean, approved fuel can.
3. Add the full measured amount of oil, then top off with the remaining gasoline.
4. Seal the can and give it a good shake. The mixture should look uniformly tinted, with no oil streaks swirling on top.

Brand-Specific Oil vs. Any Other Oil

This is where ratios diverge. Both makers also offer a ready-mixed fuel—STIHL’s MotoMix, for example—which eliminates measuring entirely and stores longer than fresh-mixed fuel.

If you’re buying a new saw and want the easiest fueling routine, the fuel mix matters less than the saw itself. Our roundup of the best gas chainsaws covers models that handle everything from light trimming to full-day felling.

The table compresses the common guidance, but the manual for your specific model trumps all of it. Mixing fresh fuel for each session—rather than storing a big batch for months—keeps the carbs clean and the saw starting on the first pull.

What Happens When You Skip the Manual

Running an unverified ratio produces two failure modes. Too much oil leaves carbon buildup on the piston and a rough idle. Too little oil starves the bearings and can seize the motor mid-cut. Neither is a fun repair.