Buy 10W-30 engine oil

Where 10W-30 is specified

Three groups of vehicles run this grade:

• **Imported cars from Japan and the USA.** There the manuals classify by API and ILSAC, and for years 10W-30 was the standard specification for naturally aspirated petrol engines. On vehicles of that origin it is often still in the service book, even where European models of the same brand moved to 5W-30 long ago.
• **Older European petrol engines** without a Longlife specification, for which the manufacturer names a 30-grade oil with a classic additive package.
• **Commercial vehicles and stationary engines** where 10W-30 is approved as the more economical alternative to 15W-40.

The difference to 5W-30 and 10W-40

Against 5W-30: identical behaviour in a warm engine, poorer cold-start behaviour. Where both are approved, 5W-30 is the better choice for a European winter - the extra cost is small and the benefit is real.

Against 10W-40: same cold start, thinner at operating temperature. An engine with high mileage and oil consumption runs more quietly on the 40 grade; an engine whose manufacturer explicitly calls for a 30 should not be switched to a 40, because the oil pump and the hydraulic components are designed around it.

Approvals and markings

With this grade, pay particular attention to where the specification comes from: if the manual gives an API category (API SP, SN) or ILSAC GF, the vehicle comes from the American or Asian market. If it gives an ACEA class or an OEM number, it is classified in European terms - and then 10W-30 is rarely the answer.

Vehicles with a particulate filter additionally need a low-ash oil; in this grade that is the exception, so check for a C approval before you put a 10W-30 into a vehicle with a filter.

On imported vehicles, watch the unit in the service schedule: miles, not kilometres. And watch the oil quantity, which on Japanese four-cylinder engines is often under four litres - there a 5-litre container covers one change plus reserve.