As mechanics, there are certain "things" that are almost impossible to explain—not because of their complexity alone but because they embody concepts that take years of practice and study to truly grasp.
Engine oil is one of those "things."
If you're a car nut, an apprentice, or even a seasoned mechanic, you probably know that oil has five key functions:
Reduce friction and wear
Prevent rust and inhibit corrosion
Clean and prevent oxidation
Provide cooling
Form a seal
But what do these really mean? Let’s break them down.*(we know, we missed 1 - see below)
Prevent Rust and Corrosion
This one’s relatively straightforward. When you coat steel with oil, it doesn’t rust. That’s because oil forms a protective layer, shielding metal from oxygen.
Inside an engine, most components are made from metals like steel, iron, and aluminium. Unlike aluminium, which forms its own protective oxide layer, steel and iron are particularly prone to rust, which can wreak havoc on tolerances and even seize components.
Circulating oil ensures that a barrier is always in place, preventing oxidation and corrosion while keeping the engine in working order.
Clean the Engine
Engine oil also functions as a cleaner. This gets a little more complicated, but for now, know that modern engine oils are formulated with detergents and dispersants. These additives help lift clean sediment, sludge, and other contaminants, preventing them from settling in, or gunking up the engine. This is especially important as oil sludge (gunk) can restrict the flow of oil which effects all of the other items on this list massively.
Additionally, oil contains anti-foaming agents to stop bubbles from forming, ensuring consistent lubrication and heat transfer.
Cooling the Engine
Here’s an often overlooked but critical function of engine oil. Most people associate engine cooling exclusively with the coolant based cooling system—radiators, fans, and thermostats.
However, engine oil plays a crucial role in handling the immediate heat generated by the moving parts.
Oil absorbs heat from components like pistons and bearings, carrying it to the oil sump where it disperses into the surrounding metal or into the water jacket. This thermal transfer allows the coolant to handle the rest. Without this process, engine components would overheat far quicker.
Forming a Seal
This one might sound strange, but liquid oil forms seals within the engine. It helps fill microscopic gaps between components, ensuring proper compression and preventing leaks. Think of it as the unsung hero of efficient combustion.
One example of this is around the piston rings. The pistons and rings themselves are a fairly tight fit in the cylinder by themselves, but forming an air tight seal for the combustion process is difficult no matter what the circumstance. By using a small film of oil, we can create an almost perfect seal around the rings which can be renewed with every rotation of the engine.
Reducing Friction and Wear
Now we get to the main event: reducing friction and ensuring lubricity.
When you think about the sheer number of moving parts in an engine—pistons, camshafts, crankshafts, valves—it’s incredible how much wear and tear they can endure. Without oil, metal components would grind against each other, generating heat, causing deformation, and eventually leading to catastrophic failure.
Engine oil creates a thin film between surfaces, preventing metal-to-metal contact. This reduces friction, minimises wear, and extends the life of every moving part in the engine. Contrary to more common situations, engine bearings don't rely on the bearing for movement at all and instead use this small film of oil around the bearing to float the part and reduce friction.
It’s not just about protection, though. High-quality oil optimises performance by ensuring smoother operation, better fuel efficiency, and more consistent power delivery.
Why This Matters
At its core, engine oil is the lifeblood of your car. Whether it’s preventing corrosion, cooling the engine, or reducing friction, every function works together to keep your car running smoothly and efficiently.
For more insight into the oils that Kashy Australia uses, check out our blog: What Oil Do I Use In My Car?
The next time you check your oil or book a service, remember: it’s not just about “topping up” or hitting that mileage mark. It’s about maintaining one of the most crucial systems in your vehicle.
If you're due for an oil change or want to know more about the right oil for your car, book a service with Kashy today.
If you have any questions about this blog post, would like a second opinion from a mechanic or would like to find an honest mechanic in Brisbane, check out Kashy here.
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