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This is the Gas and Oil Mix Craftsman String Trimmers Use

Craftsman offers string trimmers with 2-cycle and 4-cycle engines. Knowing the type of engine on your string trimmer will keep you from adding the wrong fuel and potentially damaging the engine.

String trimmers use unleaded gasoline with a minimum 89-octane rating and a maximum ethanol content of 10%.

  • Craftsman string trimmers with 2-cycle engines require gas mixed with 2-cycle engine oil at a ratio of 50:1
  • Craftsman string trimmers with 4-cycle engines have separate fill ports. One for gas and one for engine oil.

If you are unsure what type of engine is running on your trimmer, refer to your operator’s manual.

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Old or Bad Gas in a Craftsman String Trimmer

Gas is often the underlying cause of a problem that has developed in your string trimmer. It can contribute to issues with starting, dying, or a loss of power.

Gas can begin to break down as soon as 30 days after purchase. The ethanol found in most gasoline naturally attracts moisture to the fuel system.

This moisture and ethanol mixture leaves behind varnish and gummy deposits that can restrict fuel flow and cause component failures. It is often the reason why a carburetor fails.

Ethanol is added to gas to make it more environmentally friendly since it is developed from high-starch content plants like corn. While this product is better for the environment, it is not good for a small engine.

Because gas breaks down quickly, it is important to use fresh gas. Add a fuel additive like Sea Foam Motor Treatment to stabilize gas and reduce moisture so it lasts a little longer.

Craftsman string trimmers require unleaded gasoline with a minimum octane rating of 89 and a maximum ethanol content of 10% (E10). If your trimmer has a 2-cycle engine, mix a 2-cycle premium oil with the gas before adding it to the fuel port.

Avoid gasoline that includes ethanol contents greater than 10% including fuels sold as E15, E30, or E85. These fuels contain up to 15%, 30%, and 85% ethanol respectively. Ethanol-free fuels are best and will reduce the issues you experience due to old fuel.

Gas and Oil to Use in a 2-Cycle Craftsman String Trimmer

2-Cycle Gas and Oil Mix

All 2-cycle string trimmers require a 2-cycle premium oil to be added to gas before adding it to the fuel tank. Don’t make the mistake of adding straight gas to your 2-cycle string trimmer.

This will cause the engine to seize up and no longer run. This is because gas runs very dry. Without the lubrication provided by the addition of oil to the gas, the internal parts of the engine won’t be able to move freely.

Most likely, if you accidentally add straight gas to your string trimmer and start it, you will have to replace it with a new one. The engine will be damaged beyond repair.

Your Craftsman 2-cycle string trimmer uses a gas and oil mixture at a ratio of 40:1. This means 40 parts gas is mixed with 1 part oil. Refer to the chart below.

When creating this mix, use unleaded gasoline with a minimum octane rating of 89 (mid-grade) and maximum ethanol content of 10%. Add a 2-cycle premium oil that is ISO-L-EGD and JASO M345 FD certified like Craftsman full synthetic 2-cycle engine oil.

How to mix gas and oil for a 2-cycle string trimmer:

  • Use the chart below to determine how much fuel mix to prepare.
  • Remove the cap from an approved gas can. Add unleaded fuel (minimum 89 octane rating & maximum 10% ethanol content) to a gas can.
  • Using the chart for ounces of oil required, add the 2-cycle oil to the gas can.
  • Replace the cap.
  • Gently shake the fuel and oil until they are mixed.
  • Add to the fuel tank.

2-Cycle Craftsman Gas-to-Oil Mix

Gas to Oil Mix Ratio1 Gallon Gas2 Gallon Gas2.5 Gallon Gas
40:13.2 oz Oil6.4 oz Oil8.0 oz Oil
Craftsman 2-Cycle Gas to Oil Mix Ratio

2-Cycle Premixed Ethanol-Free Fuel

A great option to reduce fuel problems and extend engine life is using an ethanol-free fuel mix. This is an ethanol-free blend of oil and fuel that is ready to pour into your string trimmer’s fuel tank.

You won’t have to deal with the bad effects of ethanol as discussed in the fuel section. Ethanol-free fuels can be found at your local hardware store or online.

Gas and Oil to Use in a 4-Cycle Craftsman String Trimmer

Gas for 4-Cycle String Trimmer

While 2-cycle Craftsman string trimmers have been on the market for many years, you will now find Craftsman string trimmers with 4-cycle engines. These types of engines have separate ports for fuel and oil so there is no need to mix fuel and oil.

4-cycle Craftsman string trimmers require unleaded gasoline with an octane rating of 89 or higher and an ethanol content of 10% or less.

It is best to add a fuel stabilizer like Sea Foam or STA-BIL to keep the gasoline from breaking down quickly and to help reduce moisture and gummy deposits in the fuel system.

While using gasoline with a low ethanol content is acceptable, it is not the best option available. The best fuel to use in a string trimmer is an ethanol-free fuel.

Ethanol-free gas is the more expensive choice. You can find it offered at select fuel stations sold as REC-90. You can also purchase in containers at hardware stores or online for 4-cycle engines.

Purchasing in canisters is not only convenient, but it may also be a good alternative if you don’t want to deal with the potential headaches that can come from running old ethanol-based gas through a string trimmer.

Engine Oil in a 4-Cycle String Trimmer

4-cycle engines have separate fill ports for the engine oil and the fuel. DO NOT mix oil and fuel together for a 4-cycle engine. Never use 2-cycle oil in a 4-cycle string trimmer.

Oil is required to keep the engine components lubricated. When the wrong type or not enough oil is used, friction can build in the engine and overheat causing your string trimmer not to start and possibly ruin the engine.

Craftsman recommends using SAE30 engine oil.

The engine oil viscosity may need to be changed to one better suited for very hot or very cold ambient temperatures when you are using your string trimmer in these types of conditions.

4-Cycle Craftsman Engine Oil Viscosity

ManufacturerEngine Oil
4-Cycle Engine Oil for Craftsman String Trimmer

In Summary

The fuel used in your trimmer affects its performance. When fuel ages, it can cause corrosion and fuel restrictions. Follow these simple steps when choosing a fuel for your equipment:

  • Always use fresh gas and consume it within 30 days.
  • Make sure the gas contains no more than 10% ethanol.
  • Know the type of engine on your trimmer (2-cycle or 4-cycle).
    • 2-cycle: Mix gas and oil together before adding to the fuel tank.
    • 4-cycle: Use straight gas.
  • Add a fuel stabilizer so your gas lasts longer before breaking down.
  • Store gas in a dry location away from moisture and combustible products.