Oil and Gas Mixture for Small Engines
In small engines, such as those found on a weed whacker, gasoline is mixed with two cycle oil at a particular ratio. Typically the ratio is 40 parts gasoline to one part oil or 50 parts gasoline to one part oil. The ratio depends on the thickness of the fuel.
Inside the engine, the two-cycle oil lubricates the engine while fuel pumps through. Two cycle engines are ideal in weed whackers and other small appliances because they do not require very many chambers. The concept is similar on a larger outboard motor that requires two cycle outboard oil.