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Engine Oil Explained: Grades, Change Intervals and How to Check It

#maintenance · #engine

Engine oil is the single most important fluid in your car. It lubricates moving parts, reduces friction, carries away heat, and traps dirt and metal particles before they can cause wear. Skip or delay a change and the engine runs hotter, works harder, and wears out faster.

How to read an oil grade (5W-30, 10W-40 and friends)

The two numbers on the bottle describe viscosity, or how easily the oil flows.

  • The number before the W is cold-weather viscosity. Lower numbers flow more easily at startup, which matters on cold mornings.
  • The number after the W is the hot viscosity. Higher numbers stay thicker at high temperatures.

Always use the exact grade printed in your owner’s manual. Common grades in India include 0W-20 and 5W-30 for modern petrol engines, and 5W-40 or 10W-40 for many diesels.

Mineral, semi-synthetic or fully synthetic?

  • Mineral oil is the cheapest. It suits older, simpler engines but needs shorter change intervals.
  • Semi-synthetic blends mineral and synthetic base oils for a balanced mix of price and protection.
  • Fully synthetic offers the best protection, handles high heat, and lasts longer. It is worth the premium for turbocharged, diesel, or high-performance engines.

When should you change it?

Most petrol cars need fresh oil every 10,000 km or 12 months, whichever comes first. Diesels and turbo engines often run on shorter schedules of 7,500–10,000 km. City driving with constant stop-start traffic, dusty roads, or lots of short trips counts as “severe” use — change earlier if you fall in that bracket.

How to check the level at home

  1. Park on level ground and switch the engine off. Let it cool for a few minutes.
  2. Pull out the dipstick, wipe it clean, push it back fully, then pull it out again.
  3. The oil film should sit between the MIN and MAX marks.

If it is near MIN, top up a little at a time with the correct grade — and never overfill, which can be just as harmful as running low.

Warning signs to watch for

Get the oil checked if you notice a lit oil-pressure warning, dark or gritty oil on the dipstick, a burning smell, blue exhaust smoke, or a ticking and knocking sound from the engine. A small habit of checking your oil every few weeks can add years to your engine’s life.