How to Properly Mix Fuel for a Weed Eater

A weed eater.
  • 1-2 hours
  • Intermediate
  • 25-40
What You'll Need
Two-cycle weed eater
Measuring container
Gasoline canister

A two-cycle weed eater requires a proper mix of fuel and oil. The oil in the gasoline is the only lubrication the crankcase receives. If you don’t put in enough oil, the engine will overheat, causing it to seize. If you put in too much oil, your engine will smoke, which will gum up the muffler. A two-cycle weed eater does not have a separate reservoir for gasoline and oil, so the two must be mixed together. A correct mix of fuel and oil will keep your weed eater running smoothly and prevent engine damage.

What is the Correct Fuel/Oil Mix Ratio?

The fuel-oil mixture ratio depends upon the make and model of your weed eater. Some require a ratio of 32:1, 40:1, even 50:1. Be sure to check your owner’s manual for the proper ratio so you don’t harm the engine.

Calculating the Fuel/Oil Mix Ratio

Once you’ve determined the fuel/oil ratio for your weed eater, you can quickly calculate the amount of gasoline you need and the amount of oil you need. For example, if your fuel/oil mix ratio is 40:1, this means you need 40 part gasoline to 1 part oil. One gallon of oil is equal to 128 oz., so for a 40:1 ratio, you would divide 128 oz. by the mix ratio of 40 and see that you need 3.2 ounces of oil:

128/40 = 3.2 oz. of oil

Correct Types of Fuel and Oil to Use

When buying fuel, purchase regular unleaded gasoline and not a diesel fuel. There are alternative fuels on the market, such as ethanol or methanol. These can be used if it is made up of a 10:2 ratio.