can you use wd40 in car engine

[LeLorenzo]

No, you should not use WD-40 as a substitute for engine oil or a dedicated engine lubricant. While WD-40 is a fantastic multi-use product for loosening rusty bolts or protecting metal surfaces from corrosion, it is not designed to withstand the extreme heat, pressure, and mechanical stress inside a running engine. Its lubricating properties are temporary and thin out quickly under high temperatures, which can lead to insufficient lubrication, accelerated engine wear, and potential catastrophic failure.

The primary function of engine oil (motor oil) is to lubricate, clean, cool, and protect engine components. It is formulated with a specific viscosity (thickness) and additive packages to perform under severe conditions. WD-40 lacks these essential qualities.

Where WD-40 Can Be Used Around the Engine:

• Loosening Parts: It's excellent for freeing seized spark plugs, bolts, or brackets on the engine bay before removal.
• Cleaning: It can help dissolve grease and grime on non-hot surfaces like the engine cover or plastic components.
• Moisture Displacement: Spraying a small amount on electrical connections like battery terminals can help prevent corrosion (after disconnecting the battery).

The Critical Risks of Using WD-40 Inside the Engine: Using WD-40 in place of oil or as an "engine flush" is risky. It can dilute the existing oil, reducing its lubricity. When the engine starts, the WD-40 burns off, leaving critical components like piston rings and bearings vulnerable to metal-on-metal contact. The product's chemical composition is not meant for combustion and could damage sensors like the oxygen sensor or catalytic converter over time.

Engine Oil	WD-40
Formulated for high-temperature lubrication	Lubrication breaks down under high heat
Contains detergents to clean engine internals	Lacks engine-cleaning additives
Specific viscosity grades for engine protection	Thin, light viscosity unsuitable for engines
Designed to be circulated by the oil pump	Not designed for oil pump circulation
Withstands extreme pressure between parts	Fails under extreme pressure, causing wear

Stick to the manufacturer-recommended motor oil for your engine. For cleaning internal components, use a proper engine flush product designed for that specific purpose.

[DelCharlotte]

Look, as a guy who’s been fixing cars in his garage for 20 years, I’ve seen this tried. Don't do it. WD-40 is for squeaky hinges and rusty nuts, not for the inside of your engine. It’s like using water instead of coolant—it might seem like it works for a second, but you’re asking for a blown engine. It just doesn’t have the guts to protect your bearings and camshafts when things get hot. Use the right oil. Always.

[VanJosie]

Think of your engine oil as your car’s blood. It’s a specially formulated fluid that keeps everything running smoothly. WD-40 is more like a band-aid. It’s great for a quick fix on the outside, but putting it into the engine’s circulatory system is a bad idea. It doesn’t have the right thickness or protective chemicals, and it will burn off, leaving your engine’s vital parts without protection. It’s simply not worth the risk.

[Violet]

The confusion is understandable because WD-40 is a lubricant. However, not all lubricants are created equal. Engine oil is a high-performance fluid engineered for a specific, brutal environment. Using WD-40 inside the engine would be like using cooking oil in a high-performance race car—it might lubricate for a moment, but it will quickly fail, leading to overheating and severe damage. It's safe for external bolts and hinges, but keep it far away from your oil fill cap.

[McAdeline]

My advice is to check your owner’s manual. It will specify the exact type and weight of motor oil your car’s manufacturer requires. That oil is the result of millions of dollars in engineering to ensure your engine lasts. WD-40 is a chemical spray with a different, less durable purpose. Using it in the engine voids the protective film of real oil, potentially causing scoring on cylinder walls and leading to expensive repairs. Always use products for their intended purpose.