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Which engine oil is right for my car? 5W-30, 10W-40 and more explained
Updated 26 Oct 2026
The right oil protects your engine. The wrong one, or an old one, wears it out faster.
Read the numbers
In 5W-30, the 5W describes how well the oil flows when the engine is cold, and the 30 how thick it is when the engine is hot. Your owner's manual, or the oil filler cap, says which grade your engine needs. Using a much thicker or thinner oil than specified can reduce protection.
Synthetic or mineral?
- Fully synthetic: best protection in heat and long intervals; required by many newer engines.
- Semi-synthetic: a middle ground for many everyday cars.
- Mineral: fine for some older engines if the manual allows it, but change it more often.
Also check the quality standard on the bottle (such as an API or ACEA rating) matches your manual.
How often to change it
Lagos-style traffic, short trips, heat and dust are hard on oil. If you drive like that, use the shorter interval in your manual. Log your changes in the service log and it will remind you when the next one is due.
Check the level yourself
With the car on level ground and the engine off for a few minutes, pull the dipstick, wipe it, push it back fully and pull it again. The oil should sit between the two marks. Top up a little at a time.
Avoid fake oil
Buy sealed containers from established sellers, check the seal and printing, and be wary of prices far below normal. See how to spot fakes.
Quick answers
What does 5W-30 mean?
The first number with W is how easily the oil flows when cold (lower flows better at start-up). The second number is its thickness at engine temperature. Use the grade in your owner's manual.
How often should I change my engine oil?
Follow your manual. Many cars need it every 5,000 to 10,000 km or 6 to 12 months. Heavy traffic, short trips, heat and dust count as severe use, so lean towards the shorter interval.
General guidance only. Every car is different, so follow your owner's manual and ask a qualified mechanic.