Should I drain the gas from my weed eater for winter?

Yes, for any storage longer than about three months. Stihl and Echo both tell owners to empty the tank and run the engine until it stops, so no mixed fuel sits in the carburettor. Premix with ethanol starts to go stale in about a month, and the small diaphragm carburettor on a trimmer is the first thing old fuel blocks.

Is it better to drain or stabilize 2-stroke fuel for winter?

For handheld tools, drain and run dry: the carburettor is tiny and the tank is cheap to refill. For outboards and anything with a large tank, stabilize fresh fuel and run the engine long enough to get the treated fuel into the carburettor, then fog it. Stabilizer only works on fresh fuel; it does not rescue stale fuel.

Does fuel stabilizer change the 2-stroke mix ratio?

No. Stabilizer is dosed separately and in tiny amounts, so a 50:1 mix is still 50:1 after it goes in. Add it when you mix the fuel, not months later, and follow the dose on the bottle.

How do I winterize a 2-stroke outboard?

Run it on stabilized fuel for about ten minutes, fog the cylinders through the carburettor until it stalls or with the fogging port, drain the float bowls if your motor has drain screws, change the lower unit gear oil, flush it with fresh water if it ran in salt, and store it upright so the cooling passages drain.

What should I do with leftover 2-stroke mix in the fall?

Use it up in another 2-stroke tool if it is less than a month old, or take it to your local household hazardous waste drop-off. Do not keep unstabilized pump-gas premix over winter for spring; it is the most common cause of a no-start in March.

How to Winterize 2-Stroke Engines: Saws, Trimmers, Outboards

To winterize a 2-stroke engine you deal with the fuel first and everything else second. There are two ways to handle the fuel: drain the tank and run the engine until it stops, so no mixed gas sits in the carburettor all winter, or fill it with freshly mixed, stabilized fuel and run it long enough to get that fuel into the carburettor. Handheld tools (chainsaws, trimmers, blowers) are best run dry. Outboards and machines with big tanks are usually stabilized and fogged. Then you clean the air filter, protect the cylinder, and store the machine somewhere dry and away from flames.

Almost every spring no-start traces back to one of these steps being skipped in the fall, which is why this guide is the other half of the spring startup checklist.

What each machine needs before storage

Machine	Fuel	Cylinder	Also do
Chainsaw	Drain tank, run dry	A few drops of oil, pull to compression	Clean bar groove and oiler holes, oil the chain
String trimmer	Drain tank, run dry	A few drops of oil, pull to compression	Clean the head and shaft, grease the gearbox if it has a fitting
Leaf blower	Drain tank, run dry	A few drops of oil, pull to compression	Clear the intake screen and cooling fins
2-stroke outboard	Stabilize and run, or drain carbs	Fog while running	Change lower unit gear oil, flush, store upright
2-stroke dirt bike	Stabilize tank, drain float bowl	Fog or oil through the plug hole	Clean air filter, oil the chain, tender on the battery if it has one

Step 1: decide drain or stabilize

Mixed 2-stroke fuel made with ordinary ethanol pump gas starts to lose its volatile fractions within about a month, and the ethanol absorbs moisture from the air in a vented tank. Over a winter that leaves varnish in the carburettor and, in a damp shed or a boat, a layer of water and ethanol at the bottom of the tank. A trimmer’s diaphragm carburettor has passages so small that a thin film of varnish is enough to stop it.

That is why the handheld makers are blunt about it. Stihl’s instructions say that for storage of about three months or longer you should drain the fuel tank and run the engine until the carburettor is dry. Echo’s storage instructions say the same. Draining costs you nothing but a tank of fuel, which on a trimmer is a few ounces.

Stabilizing makes more sense when the tank is large, when the fuel is ethanol-free or canned premix, or when the engine is hard to run dry, as with an outboard on a trailer. The rule that matters: stabilizer goes into fresh fuel, at mixing time. It slows the fuel going stale. It does nothing for fuel that is already stale, so adding a dose to a can that has sat since July is wasted.

Step 2: if you stabilize, do it properly

Fuel stabilizer is dosed on its own, separate from the 2-stroke oil, and in such small amounts that it does not change your ratio: a 50:1 mix is still 2.56 oz of oil per gallon after the stabilizer goes in. Follow the dose on the bottle; the common storage dose for the big retail brands is about 1 oz per 2.5 gallons.

Mix a fresh, small batch at your engine’s ratio and add the stabilizer to the can.
Fill the tank and run the engine for five to ten minutes. This is the step people skip: until it runs, the carburettor is still full of the old, untreated fuel.
Shut it down with the tank full, which leaves less air space for condensation.

Some 2-stroke oils, including Echo’s Power Blend X and Red Armor, contain a fuel stabilizer already. Read the bottle for the storage period it claims before you rely on it, and note that it only applies if the mix was made with that oil.

If you need a small batch for the last run of the season, the calculator handles part-gallons and litres:

Fuel → oil Oil → fuel

Amount of fuel

Equipment (optional)

Mix ratio

Custom ratio (X : 1)

Add this much oil

12.8 oz

≈ 378.54 ml

Add 12.8 oz of 2-stroke oil to 5 gal of gas at a 50:1 ratio.

Step 3: handheld tools (chainsaw, trimmer, blower)

Drain the tank into your fuel can, outdoors and away from any ignition source.
Start the engine and let it run until it stops. Then pull the starter a few more times, or try to restart, until it will not fire. That empties the carburettor.
Clean the air filter. Tap out dust; wash a foam or felt filter as the manual says and let it dry. A dirty filter left over winter is still dirty in spring.
Protect the cylinder. Remove the spark plug, put a few drops of clean 2-stroke oil (or a short burst of fogging oil) into the plug hole, pull the starter slowly two or three times to spread it, and reinstall the plug. Finish by pulling until you feel compression, which leaves the piston covering the ports.
Clean the machine. On a chainsaw, clean the bar groove and oiler holes, take the chain off and store it in a little bar oil. On a trimmer, clear grass from the head and shaft and grease the gearbox if it has a fitting. On a leaf blower, clear the intake screen and the cylinder fins.
Store it dry, off the floor, and away from the furnace or a water heater pilot light. Fuel vapour from a tank that was not fully dry is heavier than air and pools low.

The leaf blower guide notes which blowers are 4-MIX or true four-strokes. 4-MIX engines (Stihl FS 91 to FS 131, BR 600 and BR 800) are winterized like a two-stroke, because they run on premix and have no oil sump. True four-strokes with a dipstick are a different job.

Step 4: outboards

Outboards are the most expensive engines most people winterize, and the 2-stroke outboard fuel mix guide explains why fuel is the biggest risk on a boat. Before the boat comes out:

Stabilize the fuel in the portable or built-in tank and run the motor on muffs or in the water for about ten minutes so treated fuel reaches the carburettors.
Fog it. With the engine running at a fast idle, spray fogging oil into the carburettor throats until it smokes heavily or stalls. Some motors have a fogging port or a fogging procedure in the manual; use it.
Drain the float bowls if your carburettors have drain screws. On a premix motor, you can instead disconnect the fuel line and let it run until it dies, then fog through the plug holes.
Change the lower unit gear oil. Drain from the bottom plug with the top vent plug out. Milky oil means water has got past a seal, which is far cheaper to fix now than after the water freezes.
Flush with fresh water if the motor ran in salt or brackish water, then let it drain.
Store it upright, so the cooling passages and the lower unit drain completely and nothing freezes in them.

For an oil-injected motor, top up the oil reservoir before storage so condensation has less space, and in spring check the injection system before relying on it. Older premix motors simply go back to the outboard page ratio with a fresh tank.

Step 5: dirt bikes

A 2-stroke dirt bike is in between. Drain the carburettor float bowl (most have a drain screw on the bottom), and either drain the tank or fill it with fresh stabilized premix. Clean and re-oil the air filter, put a little oil or fogging oil in the plug hole and kick it through slowly, oil the chain, and put a tender on the battery if the bike has one. Fuel-injected TPI and TBI bikes have no float bowl; follow the manual’s storage procedure and keep the oil reservoir full.

What to do with the leftover mix

Most people finish the season with a part-filled can. If it is under a month old, burn it in another 2-stroke tool. If it is older, or you cannot use it, take it to a household hazardous waste drop-off; never pour it on the ground or down a drain. And when you mix again in spring, size the batch to what you will use: at 50:1 that is 2.56 oz per gallon or 20 ml per litre, and the measuring tools guide covers smaller cans and ratio bottles that make a one-gallon batch easy.

When to do it

Do it after the last real use, not on the first frosty morning. For lawn tools that usually means after the final leaf cleanup; for boats, before the first hard freeze. A machine that is put away dry, oiled and clean in October is one that starts on the second pull in spring, and the how to mix 2-stroke fuel guide has the fresh-batch routine for when that day comes.