Ellie Dyer-Brown
Friday July 25 2025
3 min read
Cars aren’t supposed to burn oil, but it does occasionally happen – this guide explains why.
Why is my car using so much oil?
Excessive oil consumption is usually caused by worn-out engine parts that have started to leak oil. In some cases, oil may enter the combustion chamber and get burned along with fuel.
How to tell if your car is burning oil
It’s usually easy to tell when a car is burning oil because the following symptoms will be present:
A burning oil smell
The bluish exhaust smoke will be most visible when the engine starts and during acceleration. Misfires can happen due to oil residue coating the spark plugs.
If you’ve noticed one or more of these symptoms, your car may be burning oil. However, it’s best to book a diagnostic test to confirm the problem before arranging a repair.
Five reasons why a car burns oil
We’ve established that cars often burn oil due to a leak, but what engine parts could be responsible? Let’s take a look.
1. Worn piston rings
Piston rings are responsible for sealing the combustion chamber and transferring heat from the combustion process. Crucially, they also regulate the amount of oil between the piston and the cylinder wall. When they wear out, oil can enter the combustion chamber, where it gets burned.
2. Worn valve seals
It’s a similar story with the valve seals, which stop oil from leaking into the valve guides and combustion chamber. Old seals can allow oil to be burned, especially when the engine is cold.
3. Worn cylinder walls
If the cylinder walls become worn, the piston rings may no longer form a seal, allowing oil to bypass the piston rings.
4. Malfunctioning PCV valve
A positive crankshaft ventilation (PCV) valve is a one-way valve that removes unwanted gases from the crankcase. It helps to reduce emissions, maintain optimal engine performance and prevent oil leaks.
When the PCV valve malfunctions, it can cause a vacuum or excessive pressure in the crankcase, forcing oil past gaskets and seals and allowing it to enter the combustion chamber.
5. Worn head gasket
The head gasket seals the combustion chamber, preventing oil and coolant from entering it. When it wears out, it can allow oil to be burned in the engine – but that won’t be the only sign that the head gasket has gone. This guide discusses what to look out for.
What repair is needed for a car that burns oil?
Any worn-out parts that are allowing oil to enter the combustion chamber must be replaced. However, they must first be identified, which can be a challenging task.
When you book a fluid leak repair on FixMyCar, the quote you receive will likely be for a diagnostic test. Instead of guessing where the leak is coming from, a diagnostic allows the mechanic to locate the source and provide an accurate price estimate for the repair.
This guide provides a more detailed explanation of why mechanics sometimes quote for diagnostics.
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- Related topics:
- Diagnostic
- Diagnostics
Ellie is FixMyCar's Content Manager. She has over three years of experience writing about cars and regularly collaborates with automotive experts to provide trustworthy advice for drivers that is easy understand. Her work has been featured in Yahoo! Finance, iNews, The Daily Express and The Sun. She has a BA in English literature and an MA in creative writing from Durham University. Outside of work, Ellie follows F1 and eagerly awaits Ferrari's next era of dominance in the sport. She drives a Suzuki Swift.