Engine oil is the cheapest maintenance item you'll buy and the most expensive one to neglect. The wrong viscosity, or a change postponed by a few thousand kilometers, can cost you an engine. This guide explains how to read oil specifications and set a change interval instead of guessing.
The manufacturer specifies the viscosity and specification for your exact engine, and that's the first reference. A seller's suggestion, or "what everyone uses", may suit a completely different engine. If the manual isn't available, the information is usually printed on the oil filler cap or a sticker under the hood.
A grade like 5W-30 describes the oil's behavior at two temperatures: the number before the W indicates how freely it flows when cold (lower = faster flow on a cold start), and the number after it indicates its thickness at operating temperature. Thicker isn't automatically "stronger" — an oil heavier than the manufacturer's recommendation can slow oil delivery to tight engine tolerances, especially on a cold start.
More expensive isn't automatically more correct: a high-mileage older engine often runs better on what its manual specifies than on the highest grade available on the shelf.
A stated change interval assumes normal operating conditions. Heavy city use with frequent short trips, unpaved roads, or high summer heat all shorten the oil's real service life. The practical rule: go by whichever comes first, the recommended distance or the time interval — oil ages even if the car barely moves. The full picture is in the car maintenance schedule guide.
Changing the oil while keeping an old, saturated filter throws away half the benefit. A filter is a relatively cheap part and never one to buy used. Confirm the correct filter number for your model before buying — a similar shape doesn't mean it fits.
Oil is one of the most commonly counterfeited products. Check the seals, the label, the print quality, and the batch number, and buy from a seller you can go back to afterwards — not from an anonymous offer priced far below the market. The common signs of a fake are covered in the counterfeit parts guide.
Checking the dipstick every couple of weeks — engine cold, car on level ground — catches a consumption problem or a leak before it becomes a failure. A level that keeps dropping between changes is a signal worth investigating, not just topping up.
| What you see | What it means | Why it matters |
|---|---|---|
| 5W-30 and similar | Viscosity grade: the figure before the W is cold, after it hot | Must match what your manufacturer specifies |
| An API or ACEA standard | The oil's performance level and specification | Oil below the required level shortens engine life |
| Fully or semi-synthetic | The nature of the oil's formulation | Affects the change interval and the price |
| Production date | The age of the container | Oil degrades in long storage |
| The state of the seal | Whether the container is intact | A broken seal or a label over a label is reason to refuse |
Oil is among the most commonly counterfeited products — see our counterfeit parts guide, and organise change intervals within your service schedule. Browse the parts listings.
The right viscosity, a new filter, and sticking to the interval protect an engine better than any additive. Browse parts and oil listings on Auto Bazar and filter by your car's make and model to land on compatible products directly.
In a grade like 5W-30, the figure before the W describes cold behaviour and the one after it hot. Add to that the API or ACEA standard setting the performance level, and whether it is fully or semi-synthetic, which affects the change interval and price.
The viscosity grade and required standard are set by the manufacturer and found in the owner's manual. Oil below the required level shortens engine life however attractive the price.
Oil is among the most commonly faked products. Check print quality on the container and any spelling error, confirm the seal is intact with no label over a label, read the production date, and buy from a source you can return to.
Browse related listings
