The oil system on a Stihl chainsaw lubricates the engine and the bar and chain. With speeds over 10,000rpm's, these engines and chains undergo a lot of stress and friction, which can heat up the engine and destroy many internal parts. For this reason, maintaining proper lubrication to the engine and the bar and chain is critical.
Different than four-cycle and automotive engines, Stihl chainsaws get their lubrication straight from the fuel source. In cars and snowmobiles, the oil is either inserted directly into the crankcase or an oil pump sends it in. For a chainsaw engine, the gasoline is mixed with a two-stroke air-cooled engine oil. When the gas reaches the cylinder and gets ignited, the oil-rich fuel will also lubricate the piston and the crankshaft, which allows the piston and the crankcase to receive the proper lubrication to keep moving at high speeds.
The bar and chain on a Stihl chainsaw reaches speeds of up to 50 feet per second. These high rates of speed require a constant supply of oil to lubricate the bar and chain. Stihl chainsaws use a specially manufactured oil specifically designed for lubricating chainsaws. These oils are designed to withstand the higher heats and frictions while staying on the chain when it's spinning. For this reason, you can't use any other type of oil to lubricate the bar and chain.
The bar and chain oil on a Stihl chainsaw originates from the oil tank on the same side as the gas tank. When the crankshaft and piston reach a high enough speed to engage the clutch and chain, the oil pump also gets activated. These piston-driven pumps work much like the engine does, using vacuum pressure to suck and push the oil from the tank onto the bar and chain. After it leaves the pump, an oil delivery hose pushes it through the bar's oiler holes where the chain picks it up.
Automatic Flow Control
Stihl chainsaws use an automatic oil pump, which means that whenever the engine reaches a high enough speed to engage the chain, the pump is also activated, taking the hassle out of manually trying to engage the oil pump and control the flow of oil to the bar. However, these systems do offer an adjustable screw that allows the operator to regulate the amount of oil flowing from the pump to the bar.