Oil additives can be used to enhance the performance of oil, reducing heat and friction on the moving parts of the engine. They can also be used to stop leaks resulting from the drying out and shrinking of seals, or to clean the oil system. Using an oil additive is a great way to protect the investment you have made in your car by keeping the engine clean, free from friction and heat and stopping any leaks. The engine is a delicate machine and taking steps to maintain it is the best way to ensure a long life and efficient performance from your car.