When a car burns oil, it means engine oil is entering the combustion chambers and being burned along with the fuel. This is a sign of internal engine wear and should not be ignored. The most common symptoms include blue or grayish smoke from the exhaust, a burning oil smell, and a consistently low oil level between changes.
The primary culprits are often worn piston rings or valve stem seals. Piston rings seal the gap between the piston and the cylinder wall. When they wear out, oil can sneak past into the combustion area. Valve stem seals prevent oil from leaking down the valve stems into the cylinders; when these harden and crack with age, oil consumption increases.
Other potential causes include worn cylinder walls or issues with the Positive Crankcase Ventilation (PCV) system. A clogged or faulty PCV valve can increase pressure inside the engine, forcing oil into places it shouldn't be. While some oil consumption is considered normal for high-mileage engines (typically up to one quart per 1,000-1,500 miles), rapid loss is a red flag.
Addressing this issue promptly is crucial. Ignoring it can lead to damaged spark plugs, clogged catalytic converters, and reduced engine performance. A trusted mechanic can perform a compression test or a leak-down test to pinpoint the exact cause. The repair complexity and cost vary significantly, from a simple PCV valve replacement to a major engine overhaul.
| Common Causes of Oil Burning | Typical Repair Cost Range (Parts & Labor) | Likely Vehicle Mileage When It Occurs |
|---|
| Faulty PCV Valve | $100 - $250 | Any mileage, often overlooked |
| Worn Valve Stem Seals | $800 - $2,000 | 100,000+ miles |
| Worn Piston Rings | $1,500 - $3,500+ | 150,000+ miles |
| Worn Cylinder Walls | $3,000 - $5,000+ (often requires engine replacement) | 200,000+ miles or due to poor maintenance |
