Engine oil viscosity explained: what 0W-20 and 5W-30 mean

Reading an SAE oil grade, and why the capacity figure includes the filter.

Reading the grade

An SAE multigrade such as 5W-30 has two parts. The number before the W ("winter") rates how the oil flows when cold: lower numbers flow more easily at start-up. The number after the dash is the viscosity at normal operating temperature (100 °C): higher numbers are thicker.

A 0W-20 and a 5W-20 are equally thick when hot; the 0W-20 flows better on a cold start.

Use the grade your manual lists

Modern engines are designed around a specific viscosity, and many manuals also call for an approval or specification (API SP, ILSAC GF-6, or a maker's own standard such as GM dexos or a Chrysler MS number). Diesel engines usually need a diesel-rated oil.

Capacity

The capacities we list are the refill amount with a filter change, as printed in the source. Add oil gradually and check the dipstick, since some oil always stays in the engine.

Look it up by vehicle

Last reviewed 2026-10-14.

More guides