Why is my engine using oil? Causes and fixes

How much oil consumption is normal?

Many carmakers accept up to around half a litre per 1,000 km for engines with some mileage; healthy new engines use far less. Check your owner’s manual for the exact figure and check the dipstick every two weeks.

Where does the oil go? Two main routes

• External leaks: valve cover gasket, crankshaft seals, sump gasket or a loose oil filter. Spots under the car and a burning smell from the exhaust are the signs.
• Internal burning: oil slips past worn piston rings or hardened valve stem seals into the combustion chamber. Blue exhaust smoke, especially at start-up or under acceleration, is the giveaway.

Other common causes

• The wrong grade: an oil thinner than the manufacturer recommends passes the rings more easily in a worn engine.
• Evaporation: low-quality oils with high volatility evaporate at high temperature and are lost through the crankcase ventilation (PCV) system.
• Turbocharger seals: a worn turbo can push oil into the intake.
• Hard driving: high revs and heavy loads naturally increase consumption.

What should you do?

Start with external leaks — they are the cheapest fix. If there are none and you see blue smoke, a compression and leak-down test will find the cause. Until then, use the grade in your manual and keep checking the level. In high-mileage engines a slightly thicker oil within the manual’s range (for example 10W-40 instead of 5W-30) can reduce consumption, but it does not replace a repair.

Running low on oil is more dangerous than using it. Low oil overheats and wears the bearings, so top up as soon as the level reaches the lower mark.