Does Engine Oil Prevent Rust? What You Need to Know!

Contrary to popular belief, motor oils do not naturally prevent rust. To achieve this effect, they need to be specially formulated with specific rust inhibitors in the proper concentration.

It is safe to say that engine oil is an integral part of every engine, whether it’s a passenger car, tractor or truck. Not only does it protect against rust and corrosion but it also keeps internal parts lubricated as well as keeping piston rings in good condition.

What is Motor Oil Made Of?

Does Engine Oil Prevent Rust

Let’s start by saying that motor oil is composed of base oils and additives. Generally speaking, 70-90% of the formula consists of these base oils which come from natural gas or crude oil sources.

At least 10-30% of these additives are chemicals used as detergents, friction modifiers, antioxidants, corrosion inhibitors and viscosity index improvers.

It is best to keep in mind that conventional and synthetic motor oils both contain additives. Synthetics add oxidation inhibitors to help slow down the lubrication process over time, prolonging their shelf-life while also helping prevent rust.

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How Does Rust Form?

Rust is the result of an extended chemical reaction between iron or an alloy containing iron and oxygen and water. This reaction results in the formation of hydrated iron oxide (Fe2O3), a reddish-orange substance commonly referred to as “rust.”

However, not all rust looks exactly the same. Sometimes it can be green, such as on a sunken ship; or it may be made up of chloride ions – an ion that reacts strongly with iron when exposed to water.

Should You Use Motor Oil For Rust Prevention?

Engine oil with anti-rust and corrosion inhibitors is capable of creating a protective layer that sticks to metal surfaces for maximum protection, particularly when engines sit idle for extended periods. This layer is especially essential during periods of prolonged engine inactivity.

Rust is the result of multiple chemical reactions that take place under your bonnet, impairing vehicle performance. These can include fuel contamination, water, acids and oxygen.

You should never ignore rust as it can lead to major engine performance issues such as overheating and blocked oil/fuel filters. In order to combat corrosion, make sure your engine is regularly cleaned and lubricated, using quality oils and lubricants.

How to Prevent Rust From Attacking Metal Parts?

Rust is an unpleasant enemy of metal parts, slowly eating away at them over time. While you cannot always prevent it, there are ways to keep metal surfaces free from corrosion.

In short, rust occurs when metal comes into contact with oxygen and moisture. Water acts as the catalyst for this oxidation process.

This process breaks down the surface of metal to form an iron oxide layer. As this oxide is larger than its molecule containing it, it lifts up and separates from below, eating away at it from below.

When your car or engine has parts exposed to air and water, WD-40 is an essential lubricant to help prevent them from rusting. Not only will this protect your vehicle from rust, but any rusted areas can be repaired rather than having them replaced. This simple step ensures that rust never occurs on the inside of the vehicle.


You might be wondering, does engine oil prevent rust? Well, the thing is that motor oil, unlike other lubricants, does not prevent rust directly. In order for it to achieve this effect, it must be mixed with rust inhibitors.

Rust and corrosion inhibitors in motor oil create a protective layer that adheres to metal surfaces, providing maximum protection from rust and corrosion. This is particularly essential for engines that sit idle for extended periods.