How to choose the correct motor oil for your vehicle
Lubrication, cleaning, stopping corrosion: motor oil is essential for your vehicle to run smoothly. But how do you choose the right engine lubricant? What are the key criteria? From whether you should use mineral or synthetic oil, to what viscosity index you should look for, in this guide we explore all the factors you should consider in order to choose the correct motor oil for your vehicle.
Choosing a motor oil: synthetic or mineral?
When choosing a motor oil, you must first know the type of oil you need. Mineral oils come from the refining of petroleum, while synthetic oils are obtained by mixing several synthetic compounds and additives, with semi-synthetic oils being a blend of mineral and synthetic oils.
Viscosity – also known as the oil’s grade – is the index that defines the capacity to resist oil flow when hot and when cold. Engine temperatures can reach as high as 400°C, so this is a key criterion when choosing your product.
Marked as follows on the oil container – 00w00 – the number on the left is the low-temperature viscosity. The lower the number, the more efficient the product is at low temperatures. The number on the right indicates oil performance when hot. The higher the number, the more efficient the oil is when subjected to high temperatures.
Obtained by refining petroleum, mineral oils are generally used on conventional engines, older vehicle models and engines without turbochargers.
They are thicker than synthetic or semi-synthetic oils and are recommended for driving in temperate climates (they are not compatible with extreme temperatures), and their oxidation stability is lower than for other types of motor oils, so they need to be changed more frequently than synthetic oils. The main advantage of mineral oils is their lower cost.
These are a blend of mineral and synthetic oils – by adding synthetic oil to mineral oil, performance and engine protection levels are improved. Semi-synthetic oils therefore offer a good quality-to-price ratio, as their use does not affect the frequency of oil changes.
Chemically modified to increase their performance, synthetic oils contain fewer impurities than mineral oils and are therefore of better quality. They are designed for high-performance engines, making them more suitable for more modern vehicles and motorsport.
Synthetic oils facilitate cold engine starts while withstanding high operating temperatures, as well as optimising engine maintenance. With them, you can go longer between oil changes, for both diesel and petrol engines.
Understanding motor oil standards
When choosing a motor oil, you can also refer to the standards of the product. This information allows you to understand:
the type of engine the motor oil is designed for (diesel or petrol).
its performance level.
if the oil meets your automotive manufacturer’s recommendations.
On the current market, three standards are used to describe motor oils:
The ACEA standard
This is the standard of the European Automobile Manufacturers' Association. It is a quality indicator that is determined by a letter and a number (e.g. A1). The letter indicates the type of engine:
A – oil designed for petrol engines.
B – oil designed for diesel engines in private cars.
C – for light engines equipped with catalytic converters or particulate filters.
E – for commercial vehicles and trucks.
The number indicates the specific performance the oil must provide. The higher the number, the greater the oil’s performance..
The ACEA’s 2016 guidelines define:
Three category combinations for petrol and diesel engines: A3/B3, A3/B4, A5/B5.
Five categories for vehicles with a pollution control device: C1, C2, C3, C4, C5.
Four categories for commercial vehicles and trucks E4, E6, E7, E9, of which two are for vehicles with a pollution control device: E6 and E9.
The SAE standard
Determined by the Society of Automotive Engineers, this standard describes the degree of oil viscosity. It is indicated on the front of the container: the 00w00 index.
The API standard
Established by the American Petroleum Institute, it classifies the product according to several criteria: dispersive power, and protection against wear, oxidation, corrosion and detergents. The standard consists of two letters: S for gasoline petrol engines, or C for diesel engines. The second letter indicates the oil’s performance. The “further” the letter is in the alphabet, the higher the quality of the oil. For example, an SH oil will have a lower performance than an SN oil.
To know the standard required for your vehicle, see your vehicle owner’s handbook or get advice from a professional. To learn more about the best lubricants available for your engine, view our range of automotive engine lubricants or contact our team.