What does oil do?
Put simply, oil protects and maintains the engine.
Oil lubricates the engine components. It decreases friction between the parts – which ultimately reduces wear and tear. And if less friction is produced, less heat is produced. That means there’s a lower risk of the engine overheating.
Oil can also help keep the engine clean. A constant flow of oil carries dust and residue to the oil filter. Without oil, this residue would eventually build up and clog the engine components.
But just pouring in any oil isn’t enough – and using the wrong oil could do more harm than good. The oil you’ll need depends on your car’s engine. And there are a few different factors that decide which is best…
Oil grades
Oil grade is shown in numbers – you’ll find yours in the car manual or online, and it’ll match up to grades on oil bottles. The grade tells you how viscous the oil is. Viscosity describes how easily a liquid flows.
For example, honey has a higher viscosity than water. It’s thicker, stickier, and doesn’t flow as smoothly.
The majority of car oils will have two sets of numbers eg 10w-40. These oils are multigrade – they’re designed to change viscosity at different temperatures.
The first number – eg 10w – tells you how well the oil will flow at lower, winter temperatures. The lower the number, the better it flows. The second number – eg 40 – indicates how well the oil flows at higher temperatures. Again, the lower the number, the better it flows.
Most modern engines work best with thinner oil; it can flow more easily between parts and around smaller components. So most manufacturers may recommend an oil with lower viscosity (or lower numbers).
Always check the manual or with manufacturers for the recommended oil grade for your car.
Oil specifications
Different engine types need different oil specifications.
Oil specifications are set by the ACEA (European Automobile Manufacturers’ Association). Like oil grades, you can find what your car needs in the manual or online. Each oil specification is outlined by a letter and a number eg A1. The letter identifies the class of oil; the number outlines the category within the class.
For example, A1 indicates suitable oil for a fuel economy petrol engine – like a Ford Focus.
Types of oil
So you’ve got the right grade and specification – but have you picked up the right type of oil?
Many manufacturers recommend synthetic oil for newer engines. Synthetic oil is chemically modified with additives to increase lubrication, anti-corrosion, and anti-oxidation qualities. Plus, it has a stable viscosity – so it works well at high and low temperatures. Synthetic oil is more effective than other oil types at helping fuel efficiency.
Mineral oil is usually recommended for older, classic cars. It’s refined crude oil, so it’s designed for less advanced, low-performance engines. Mineral oil tends to have a higher viscosity than other oil types – it flows through engines relatively slowly. This can increase fuel consumption and impact the car’s performance. But if manufacturers recommend mineral oil for your car, it’s still perfectly suitable for your engine.
Semi-synthetic oil is a combination of the two. Semi-synthetic flows better and lasts longer than mineral oil. But it doesn’t quite match up to synthetic oil in terms of performance and engine protection. Many cars can perform better with fully synthetic oil, even if manufacturers recommend semi-synthetic.
I’ve used the wrong oil. Now what?
Nothing catastrophic will happen if you put the wrong oil in your car. Not yet, anyway. But it could cause serious problems a few thousand miles down the road.
Using the wrong oil puts added strain on engine components. Parts won’t be lubricated properly, so they could wear sooner. And ultimately, that can decrease the lifespan of your engine.
Always try to use the recommended oil to maximise engine health and lifespan. Making the mistake once should be fine. But if you use the wrong oil a lot, you might want to drain and re-fill – or get a mechanic to do it for you.
