What Is a Engine Oil?
Engine oil is a precisely formulated lubricant circulated under pressure through every moving part of the engine by the oil pump. Modern engine oils are mineral, semi-synthetic or fully synthetic, with additives providing additional protection, cleaning properties and temperature stability. Engine oil is specified by viscosity grade (such as 5W-30 or 0W-40) and by manufacturer specification (such as VW 504.00 or BMW Longlife-04). Using the wrong specification can cause serious damage.
What Does the Engine Oil Do?
Engine oil serves multiple critical functions simultaneously. It lubricates metal-to-metal contact surfaces to reduce friction and wear. It cools internal components that cannot be reached by the coolant system. It cleans the engine by suspending contaminants in suspension until they are trapped by the oil filter. It also protects against corrosion and helps seal microscopic gaps between piston rings and cylinder walls.
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Get My Free Fault Scan →Symptoms of a Failing Engine Oil
Low engine oil level causes the oil pressure warning light to illuminate — one of the most serious dashboard warnings in any vehicle. Symptoms of running low on oil include increased engine noise, a ticking or tapping from the valve train, reduced oil pressure and in severe cases complete engine seizure. Degraded oil that has not been changed causes sludge buildup, blocked oil ways and accelerated wear throughout the engine.
When Should the Engine Oil Be Replaced?
Engine oil change intervals vary by vehicle — typically every 10,000 to 20,000 miles on modern vehicles with longlife service systems, or every 12 months. Always use the exact oil specification recommended by the manufacturer. Using a cheaper off-specification oil can void manufacturer warranties and cause damage to components including the DPF and catalytic converter.
If you are experiencing symptoms related to your engine oil and are unsure whether it needs replacing, a free MotorLoom fault scan can help identify whether the component is likely at fault - giving you the most likely cause and estimated repair cost before you visit a garage.
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Related Parts
Other components that work alongside or are related to the engine oil: