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How to identify a 2-Cycle engine and determine the best oil to gas ratio

Briggs & Stratton Admin : Updated on January 15, 2026

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How to Identify a 2-Cycle Small Engine

The easiest way to determine if your small engine is a 2-cycle or 4-cycle is the number and type of fill ports (where you add either oil or gas) on the engine.

  • If the engine has a single fill port for both the engine oil and gas, you have a 2-cycle engine. The fuel cap will usually indicate 2-cycle or the fuel oil ratio. Also, Briggs & Stratton 2-cycle engines have the intake and exhaust 180 degrees from each other.
  • If the engine has two fill ports, one for gas and another separate one for oil, you usually have a 4-cycle engine. Exceptions to this rule do exist, such as 2-cycle chainsaws that have one fill for the oil/gas mix and one fill for the bar oil
  • On 4-cycle engines, oil fill caps are usually yellow in color and have the intake and exhaust on one side of the engine. Do NOT mix oil and gas in these engines.

How To Determine the 2-Cycle Engine Oil Mix

Since all 2-cycle small engines use the same fill port for both fuel and oil, a 2-cycle oil mix is necessary for your outdoor power equipment to function properly. Note: never mix oil and gas in the engine fuel tank. Only mix oil and gas in an approved fuel can. The Specific oil/gas ratio your small engine requires can be obtained in your Operator’s Manual. Once you identify your oil/gas ratio, the following chart may be helpful:

50:1 Ratio

Gasoline

1 Gallon

2 Gallons

3 Gallons

4 Gallons

5 Gallons

2-Cycle Oil

2.6 US Oz.

5.1 US Oz.

7.7 US Oz.

10.2 US Oz.

12.8 US Oz.

 

32:1 Ratio

Gasoline

1 Gallon

2 Gallons

3 Gallons

4 Gallons

5 Gallons

2-Cycle Oil

4.0 US Oz.

8.0 US Oz.

12.0 US Oz.

16.0 US Oz.

20.0 US Oz.

Still need help? Contact a Briggs & Stratton dealer for assistance.
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