All Weed Eater brand two-cycle gas trimmers use a 40:1 ratio of gas to oil. That's equal to 3.2 ounces of oil to 1 gallon of regular gas. The gas should be 87 octanes with no more than 10 percent alcohol. All Weed Eater brand two-cycle gas trimmers have a maximum operating pressure of 5 psi and an average working life of 30,000 uses.