Low Viscosity Oils — 0W-16 and 0W-8

If you have been working on cars for more than a few years, you remember when 10W-30 was the standard oil. Then 5W-30 became the norm. Then 5W-20. Then 0W-20. Now 0W-16 is standard on many new vehicles, and 0W-8 exists in some markets. Each generation, the oil gets thinner. This is not a gimmick — it is engineering driven by tighter tolerances and fuel economy regulations.

Modern engines are built with much tighter bearing clearances than older engines. The crankshaft journals, rod bearings, cam bearings, and piston-to-wall clearances are all smaller. Thinner oil flows through these tight spaces with less resistance, which means less friction, which means less fuel wasted on internal drag. The difference between 5W-30 and 0W-16 can be 1 to 2 percent fuel economy improvement across a fleet — which is worth billions in CAFE compliance for manufacturers.

Using oil that is too thick increases fuel consumption, causes the variable valve timing system to respond sluggishly (because VVT actuators rely on oil pressure and flow through small passages), and can trigger oil pressure DTCs on engines with variable displacement oil pumps. Using oil that is too thin on an older engine designed for thicker oil will cause low oil pressure, increased wear, and potential bearing failure. Always — always — use the viscosity specified by the manufacturer for that specific engine.

The ILSAC GF-6 standard replaced GF-5 in 2020. There are two versions: GF-6A covers 0W-20, 5W-20, 5W-30, 0W-30, and 10W-30 — these are backward compatible with older GF-5 engines. GF-6B covers 0W-16 only — this is NOT backward compatible. A GF-6B oil should only be used in engines designed for 0W-16. Look for the API donut on the bottle. GF-6A has the standard starburst symbol. GF-6B has a different shield-shaped symbol specifically to prevent someone from accidentally using 0W-16 in an engine that needs thicker oil.

Toyota has standardized 0W-16 across most of their lineup since the 2018 model year — Camry, RAV4, Corolla, Highlander, and many Lexus models. Honda is moving to 0W-16 on newer engines. Hyundai and Kia spec 0W-16 on some Smartstream engines. Subaru uses 0W-20 on most models. When in doubt, check the oil cap — most modern vehicles have the viscosity printed right on it.