by Kelechi Ujagbor

Engine oil is a lubricant that protects your engine from friction, absorbs heat from the combustion chambers of your engine, channels away the by-products of combustion and inhibits corrosion.

As oil heats up, it gets thinner and flows more readily. However, when the oil gets too thin, it does not stay on the surface of the metal long enough to act as a proper lubricant. So the goal of oil manufacturers is to prevent the oil from getting too thin when hot but thin enough to flow when very cold. For this reason, manufacturers designed a dual grading system that works well for hot temperature and cold temperature as well.

Engine designers typically design their engines to operate ideally at 100°c and the oil to have a weight of 10 at that temperature. The ideal engine oil weight is 10. This is why you need to warm up your engine before driving to give the oil enough time to get hot.

Most engines have a very high compression ratio that benefits from slow driving upon start up. When your car gets to 212F, the engine oil weight would be at exactly 10. Engine wear actually starts when the oil is too thick to lubricate the engine internals upon startup and gets diverted into the engine sump bypassing the engine when you step on the gas pedal.

The Society of Automotive Engineers established viscosity gradings (0, 5, 10, 15, 20, 25, 30, 40, 50 or 60) that are used to categorise oil. The numbers are marked on a typical quart of oil, for instance, 10W-30.

The number before the W is the cold viscosity rating and the number after is the hot viscosity rating. A 10W-30 oil will behave like a 10 grade oil when cold and like a 30 grade oil when hot. In a cold climate, you want a very low number before the “W” and in a hot climate; you want a high number after the “W”.

Taking Nigeria for example where Toyota is the most driven car, mechanics say that the best kinds of lubricants for the engine is 10W-30 or 10w-40 depending the region one is based. But they also advise that the latter should be used in hotter environments and the former in moderate environments. In Nigeria, you don’t need to take note of the number before the W because the weather does not get cold enough.

Sludge is what happens in your engine when the oil additives and chemicals break down and turns the oil into gunk or tar-like substance (black custard). It can occur due to prolonged oil change intervals or due to high engine heat exposure. Sludge can cause your engine to seize from oil flow block.

But if you only care about fuel economy, then you would want to buy the thinnest oil possible because there will be less restriction to oil flow in the engine, This is why manufacturers are now building for thinner oils like 5W-20 from 10W-30.

If you only care about greater engine lifespan, then you would want the thickest oil available, because it offers you more protection from severe operations and greater protection from heat.

Thicker oil can readily absorb and retain heat from the engine, but if you’re in a cold climate, this might be a problem because it might be too thick to flow through the engine when you first start the car.

YNaija spoke to a few mechanics who gave us their thoughts on the best engine oil brands for vehicles. Naturally, they all spoke in favour of the brands that they work for. Sylvanus who works as a mechanic at Conoil Filling Station, in Eric Moore, Surulere naturally cited his brand, ‘Conoil Quatro Ultra’ as the best for cars saying that it makes engines last longer. Ola at Mobil recommended ‘Mobil 1 new life’ a synthetic oil, claiming that it is efficient and the best for cars.

The first female mechanic that we interviewed, Biola, works for Forte Oil, and listed Synth 10000, Visco 2000, Super Visco Static and Heavy Duty Motor Oil as the best brands. Taju at Total claimed it is Quartz 5000, while Gbenga at Oando mentioned Oleum.