The Subaru-Robin EC10 family of engines are small, lawnmower-sized engines used in a variety of equipment. Some of these include lawnmowers and post-hole diggers. Like any internal combustion engine, it has fuel, air and oil requirements. Knowing the oil requirement is important, since adding the wrong oil or incorrect amount will result in damaging the engine.
According to the Robins Service Manual, this is a dual-oil engine. Because it is a two-cycle engine, it requires oil to be mixed into the fuel. However, unlike many two strokes, it also requires oil in the crankcase. For the crankcase oil, the engine requires 1 oz. of SAE 30 straight-weight oil.
This engine requires two fuel-oil mixes, one for the break-in period, and another for the time after break-in. For the first 10 hours of running time, the fuel-oil mix must be 20 to 1. After 10 hours of running time, the mix must be 50 to 1. The heavier oil mix is to allow the rings and other components to seat properly.
If the engine has to be stored, proper oiling is essential beforehand. First, drain the fuel tank and system completely dry. Then, drain the oil from the governor assembly. Remove the spark plug, and pour 1/8 cup of oil into the cylinder, through the spark plug hole. Replace the plug, but not the spark plug wire. Manually turn the engine over a few times, to circulate the oil in the combustion chamber. This will lubricate the inside of the cylinder and prevent rusting during storage.