In two-stroke engine bikes, oil is mixed with petrol (gasoline) for lubrication and cooling purposes. Two-stroke engines are different from four-stroke engines in terms of their operating cycle.
In a two-stroke engine, the combustion and power stroke occur in one revolution of the crankshaft, while in a four-stroke engine, they occur in two revolutions. This fundamental difference affects how lubrication is provided in these engines.
In a four-stroke engine, oil is stored in a separate oil sump, and it is circulated by an oil pump to lubricate various engine components, such as the crankshaft, camshaft, and valves. The oil is not mixed with the fuel because the fuel and air are drawn into the cylinder separately.
The engine relies on a mixture of petrol and oil for lubrication. The oil is mixed with the fuel in a specific ratio, typically 2% to 5% depending on the manufacturer's recommendations.
When the fuel-oil mixture enters the cylinder, it lubricates various parts of the engine, such as the piston, piston rings, cylinder walls, and crankshaft bearings. The oil also helps in cooling the engine by carrying away heat generated during combustion.
The combustion process in a two-stroke engine is less efficient compared to a four-stroke engine, and some of the oil in the fuel mixture is burned along with the fuel. This leads to the characteristic blue smoke that is often associated with two-stroke engines.
It's worth mentioning that the oil used in two-stroke engines is specifically formulated for such applications. Two-stroke engine oil is designed to burn cleanly, provide adequate lubrication, and minimize carbon deposits in the engine.
In summary, oil is used in two-stroke engine bikes to provide lubrication and cooling since these engines lack a separate oil system. The oil is mixed with petrol and enters the engine through the fuel intake, where it performs its lubricating and cooling functions.