Kamranmotors Shop — Engine Oil Viscosity Grades | kamranmotors.shop

Which grade should go in the engine?

Take the grade from the vehicle handbook: the winter letter-number sets cold-start behaviour, the trailing number sets viscosity at operating temperature.

A grade such as 0W-20 is two separate SAE J300 classifications joined by a hyphen. The winter part, 0W, is a cold-cranking and pumping class tested at fixed low temperatures. The non-winter part, 20, is a kinematic viscosity window measured at 100 °C.

The winter number does not describe how thin the oil is in summer; it describes how much resistance the oil offers to the starter at the coldest test temperature of its class. The trailing number does not describe cold performance; it describes the flow band at full operating temperature.

Manufacturers moved recommended viscosity downward from the mid-1980s, when it had already settled at 5W-30, mainly to improve fuel efficiency. Modern handbooks commonly specify 0W-20 or 5W-30, and the label on the bottle must match both the winter and the non-winter part of that specification.

• Read the handbook first: the specified grade is a requirement, not a suggestion.
• Match both parts of the grade — 0W-20 is not interchangeable with 5W-20 in a handbook that names one of them.
• Check the standards code on the bottle (API, ILSAC, ACEA) against the code the handbook also names.

How often should the oil be changed?

Follow the handbook interval, but treat trips under 15 kilometres as severe service that shortens it.

Honda cites 12,000 kilometres (7,500 miles) for its 5W-20 and newer 0W-20 oils. Quick-lube shops still often quote 5,000 kilometres (3,000 miles) or every three months, and that figure comes from older severe-service assumptions rather than from the handbook of a modern car.

Distance alone does not decide the interval. Trips shorter than 15 kilometres (10 miles) do not bring the oil to full operating temperature, so water and unburnt fuel stay in the sump and the oil ages faster than the odometer suggests. Such driving counts as severe service and requires more frequent changes.

The same severe-service label applies to repeated towing, long idling, dusty roads and sustained high-load running. In those cases the shorter of the two quoted figures — handbook distance or time — is the one to keep.

• Normal service: the handbook distance, up to 12,000 kilometres (7,500 miles) where the maker cites it.
• Severe service (trips under 15 km, towing, dusty roads): the shorter interval, often 5,000 kilometres or three months.
• Change the filter at every oil change; a loaded filter bypasses and feeds unfiltered oil to the bearings.

What the bottle labels actually certify

API, ILSAC and ACEA codes are dated specifications with measurable limits behind them.

The American Petroleum Institute service categories and the ILSAC GF series describe performance tests an oil must pass before it may carry the mark. ILSAC GF-6 was published in 2019 and licensed from May 2020; GF-6A is backward compatible with GF-5, while GF-6B covers SAE 0W-16 only.

Volatility is one of the measured limits. Under API SL and ILSAC GF-3 the Noack evaporation loss may not exceed 14%, and some manufacturer specifications require less than 10%. A more volatile oil burns off in the crankcase and raises consumption between changes.

European handbooks often name ACEA categories instead. ACEA A3 oils run a wider viscosity tolerance for older designs, ACEA A5 a lower-viscosity, fuel-economy oriented band; both sit alongside the API and ILSAC codes rather than replacing them.