40 To 1 Gas Oil Mix For 2 Stroke Engines

By: Leon Rhodes

2 stroke small engines generate a lot of heat. The heat dissipates into the air through cooling fins on the engine but 2 stroke engines need additional cooling help. By adding a small amount of oil to the gas overall friction is reduced and the engine runs cooler.

Trimmer Gas and Oil Mix Ratio

Most 2 stroke small engines on mowers, blowers and trimmers require a gas oil mixture ratio of 40 to 1. Some small engines, like those on Stihl chainsaws, require a 50 to 1 gas oil mixture so check manufacturer specs before mixing. This gas oil mix chart shows how much oil to add to the gas.

Gas Oil Mix Chart

Mix Ratio Gas Volume 2-Cycle Oil
Imperial Fluid Ounces
32 To 1 1 gal. 4 oz.
40 To 1 1 gal. 3.2 oz.
50 To 1 1 gal. 2.6 oz.
Metric Fluid Milliliters
32 To 1 1 liter 31.25 ml
40 To 1 1 liter 25 ml
50 To 1 1 liter 20 ml

Gas for 2-Cycle Small Engines

Modern gas powered 2-cycle engines require a small amount of oil to be mixed with the gas to prevent engine failure.

Adding too much oil will cause the engine to billow clouds of smoke from the exhaust. Adding too little oil to the gas will cause the engine to overheat causing damage from lack of lubrication.

Do 4-Cycle Small Engines need mixed gas oil?

4-cycle small engines do not need oil added to the gas, they have an oil reservoire to hold the oil. This is because they have a built in oiling system to provide lubrication and cooling.

Do not mix oil into the gas for 4-cycle engines unless the manufacturer says so. You can identify a 4-cycle engine by

Is My Small Engine 2 Stroke or 4?

The easiest way to tell if a small engine is a 2 stroke or 4 stroke is by looking for an oil reservoir on the engine. If present it will have a filler tube and possibly other markings telling you that's where the oil goes.

All small engines require oil, either in the oil reservoire or mixed with gas, so remember that oil reservoirs are on 4 stroke engines and no oil reservoire means 2 stroke engine. Only add oil to the gas of 2 stroke engines.

Pre-Mixed 2 cycle Gas

Pre-mixed 2 cycle gas is available at most hardware stores. A gas stabilizing agent is typically added to pre-mixed gas to give it a longer shelf life.

The downside to buying pre-mixed gas is that it tends to be more expensive than mixing gas and oil yourself.

Additionally, mixing gas and oil yourself allows you to control the octane and ethanol levels of the gas. Mixing it yourself is often cheaper than buying pre-mixed gas.

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