While all of your engine’s fluids are important, the vital one is oil.
With oil doing such an important job under your hood, it’s important to know a bit more about this essential fluid.
What does it do?
Oil lubricates the moving parts in your car’s engine, some of which are only a few thousands of an inch apart. It also helps to remove heat from the engine’s high-temperature combustion area, inhibits corrosion, reduces engine wear, and suspends dirt particles so they don’t settle in and clog up those moving parts.
To make engine oil, manufacturers first distill crude oil into four products according to each one’s boiling point, a process called fractional distillation. The lowest grade is asphalt. Base oil, which is the lubricating variety, is next up, followed by diesel and home heating oil, and then gasoline.
These base oils are further separated by their individual boiling points, which produce the higher and lower viscosity grades. We’ll come back to that, because it’s important. A bottle of engine oil contains about 80 per cent base oil, with the remaining 20 per cent made up of various additives such as dispersant, anti-wear agents, antioxidants, and detergents.
At one time, all engine oils were “conventional” oils, distilled and packaged straight from crude oil. Now you’re more likely to see synthetic oils on the shelf. The name sounds like they’re made from non-petroleum ingredients, but in reality, most synthetic oils are made from base oils that are distilled from crude. The difference is that synthetic oil’s base stock is of higher quality than that used in conventional oil, and it undergoes a synthesis process that produces consistently-shaped molecules for improved lubrication and flow. Fully synthetic oil also contains additives that are not distilled from crude oil.
Because both are crude-based, it’s safe to mix synthetic and conventional oils when necessary, such as topping up your engine, and it’s also safe to switch from one to the other when doing an oil change. Switching to synthetic will not cause an engine to leak or experience blow-by (when oil slips by the piston rings and into the combustion chamber).
Now … about the importance of viscosity. Oil gets thinner as it gets hot, reducing its ability to protect the engine, and becomes thicker in the cold, which can make it harder to start the engine. To get around this problem, manufacturers mix different viscosities of oil to produce multi-grade blends.
Viscosity is indicated by numbers. A lower number means oil that will remain fluid at low temperatures, while a higher number is oil that will stay thick enough when it gets hot. The percentage of higher or lower viscosity in the blend determines the optimum use for the oil.
The first number on the blend indicates the oil’s cold-weather performance, with a lower number meaning it can take colder temperatures. The W in between the two doesn’t mean Weight, as many people believe, but Winter. The number after the W indicates how well the oil handles hot weather, where a higher number is best.
What about changing your oil?
What about aftermarket oil additives?
And any time the oil warning lights up on your dash, pull over as soon as it is safe to do so, and turn the engine off. Even if the dipstick shows that it has plenty of oil, it could indicate a failure of the oil pump, which means that the oil isn’t getting to the places where it’s needed.