Engine oil is an essential element for the functioning of the vehicle. Its base oil content varies from 60 to 85%. These oils can be mineral or chemically synthesised, and generally differ in viscosity. We explain how to choose your engine oil and what viscosity to use according to your needs.
WHAT IS THE ROLE OF ENGINE OIL?
The internal combustion engines in our vehicles are made up of mechanical and metallic components that are connected to each other. To ensure their proper functioning, they need to be lubricated. This is what engine oil is used for. But not only that! Engine oil is also essential for the following actions:
Protection: Engine oil not only lubricates the components under the bonnet. It also protects them against corrosion. Leakage of liquid from the engine causes a mixture with oxygen. This oil-oxygen mixture, in combination with contact with metal parts, causes a reaction. This is the oxidation of the iron elements of the engine, which can damage it. Engine oil helps prevent this oxidation.
Cleaning: It is important to keep the engine clean. Since it is not possible to remove the engine at high frequency, it is important to find a way to clean it without any problems. The engine oil helps to capture sludge deposits and fine and metallic particles in the engine system. This allows the engine to function optimally.
Cooling: It also cools certain parts of the engine, especially those parts where the coolant is not able to do so. This is the case for the crankshaft, camshaft, pistons, etc.
THE VISCOSITY OF THE ENGINE OIL
You have probably already noticed this when buying your engine oil. The oil is provided with viscosity indices that measure its ability to remain fixed on a support. The viscosity of the engine oil is made up of grades giving the index when cold and when hot.
There are different types of engine oil. Monograde oils are divided into two categories. These oils are mainly intended for older vehicles.
- Winter use: They have the letter "W" representing the English word Winter. Examples are SAE 0W, 5W, 10W, 15W, 20W and 25W. They have a low viscosity and are therefore more fluid. They are intended for winter use.
- Summer use: Grades without the "W" designation are high viscosity and are designed for summer use. This is the case for SAE 20, 30, 40, 50 and 60.
MULTIGRADE OILS: 5W30, 15W40, 10W40
Intended for modern vehicles, multigrade oils can be used in all seasons. They therefore have two viscosity indices. You will often see 5w30 motor oil, 15w40 motor oil, 10w40 motor oil, etc., where the value before the "W" represents the winter viscosity index, and the value after the "W" represents the warm weather index.
The first grade is the cold start capability. The lower the value, the better the cold start ability. For the second grade, the higher the number, the better the engine's sealing and protection**. The lower the number, the more effective the reduction of block friction.
For optimal and quick starting, it is advisable to use an oil with low viscosity. The best way to choose your engine oil is to rely on your vehicle manual or service book. If in doubt, a professional will be able to advise you.