How do I choose the right engine oil?

Often, a manufacturer will suggest one or more viscosity values for an engine such as 5W-20 or 5W-30 based on different factors including the temperature and load. Engines often need a different viscosity depending on the operating conditions. OEMs, moreover, are adjusting their lubrication instructions faster and faster to comply with the need for green and fuel-saving alternatives. Which factors should you take into account when choosing the right engine oil?


This is a measure of a fluid's resistance to flow. In relation to engine oil, this is noted down using the usual "XW-XX" notation. The number that precedes the "W" indicates the fluid's flow at 0 degrees Fahrenheit (-17.8 degrees Celsius). The "W" stands for winter. The lower the number, the less the oil thickens in cold weather. A 5W-30 engine oil will become thinner at low temperatures than a 10W-30 grade, but will still flow slower than a 0W-30 grade. An engine in a colder climate where engine oil tends to become thicker because of the low temperatures would benefit from 0W or 5W. A car used in a very hot climate would need a higher number to ensure the oil does not thin too much.

The number after the “W” indicates oil viscosity at 212 degrees Fahrenheit (100 degrees Celsius). This number represents the oil’s resistance to thinning at high temperatures. For instance, oil with a 10W-30 grade thickens faster than oil with a 10W-40 grade. The user manual will recommend the best viscosity range and the owner can then make the right choice within these characteristics.

Engine oil types

Mineral oil: This is the oil that is used in bulk at dealers and is usually also the cheapest on the market. Most comply with API and SAE standards, but offer few options for additive packages. This is an appropriate oil for owners that trust frequent oil changes and drive few kilometres.

Synthetic blend oil: This is the standard oil for vehicles of the last decades. It is formulated in such a way that it offers better protection in relation to heavier engine loads and the related higher engine temperatures. These oils are popular with pick-up and SUV drivers because they offer better protection, but they usually cost a fraction more than conventional premium oils. Car manufacturers usually specify 5W-20 or 5W-30 oil although some need 10W-30. These three classifications refer to basically all light vehicles on the road although this changes when the engines become more accurate and pickier with regard to specific oil types.

Totally synthetic oil: These oils are made for high-tech engines. If these oils endure strict special tests (specified on their labels), this means that they deliver superior long-term performance in all critical areas ranging from the viscosity index to protection against engine deposits. They flow better at lower temperatures and retain their peak lubrication at high temperatures. Although excellent, synthetic oils are approximately three times as expensive as conventional oil and not always needed for most engines. Use the user manual as a guide.

Fuel economy oil: OEMs are adjusting their lubrication instructions to comply with the need for green and fuel-saving alternatives. Thanks to the introduction of the ACEA C5 standard, they prescribe low-viscosity engine oils more and more often (OW-XX). A lower viscosity means less friction in the engine and therefore lower energy loss. In this way, the vehicle’s fuel is converted more efficiently into the energy needed to move the vehicle. Engine oil with a lower viscosity also means a thinner lubrication film. In the past, this effectively meant reduced protection and therefore more rapid wear of the engine. However, the latest generation of engines has been modified for extremely small material tolerances. The design of the lubricant must continue to offer optimum protection in the more demanding conditions which arise.

Oil change interval

Most drivers follow the 3 month and 4,828 kilometre (3,000 mile) rule. In relation to frequent oil changes, a mineral oil should always be sufficient for a correct lubrication. Some car companies such as Mercedes-Benz and BMW only recommend using synthetic oil in their cars. The user manual for the car offers a good indication of the oil type that must be used. A good rule of thumb is also not to switch between the different types. If your car started using conventional oil, continue using it. If the car uses synthetic oil the first time, be careful if switching to conventional oil.

Euro standards

Car manufacturers must always comply with the Euro standards (that are constantly changing) and adjust their engine designs based on these standards. The Euro VI standard determines that oil must be ‘Low SAPS’ or ‘Mid SAPS’ for approved engines. This means that they have sulphated ash, phosphorus and sulphur (SAPS) in limited quantities. In turn, this ensures the sustainable character of the oil. Many engine oils is ‘Full SAPS’. This means that SAPS particles can lead to system obstruction. The best solution is therefore to choose high-quality oil that complies with the Euro VI standard.

One of the best ways to find the right engine oil for your car or truck is to use the basic recommendations of the manufacturer. Also bear in mind that changing the oil regularly and replacing the filters regularly play an important role in having the engine run in the long term. An engine that has been fine-tuned correctly can also improve fuel consumption and therefore lead to fuel savings. We therefore recommend following the recommendations of your car manufacturer about maintenance. High-quality engine oils can also make the engine run more efficiently and therefore lead to fuel savings.

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