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Buy 20W-20 Engine Oil
Which vehicle?
Enter your vehicle - we show only what belongs in it.
20W-20 is a grade from another era: the span between cold-start and operating viscosity is so narrow that it behaves almost like a monograde. It turns up in historic specifications and in a few special applications - not in modern vehicles.
What "20W-20" means
In multigrade oils the two numbers are normally far apart - 5W-30, 10W-40. If they are the same, it means the oil behaves like an SAE 20 when cold and like an SAE 20 at operating temperature. That puts it closer to a monograde than to a modern multigrade.
Two things follow in practice. First, cold-start behaviour is poor - in frost, oil pressure builds up late. Second, the lubricating film at operating temperature is thin compared with everything else engines with this specification are given. Both are the reason the grade has disappeared from the car world.
Where it still turns up
In old owner's manuals, in specifications for individual stationary and industrial engines, and in applications where a defined, unalloyed behaviour is wanted. If you find this figure in a historic handbook, check with the marque club or a specialist workshop what the correct present-day equivalent is - for classics that is either 20W-50 or a monograde of the appropriate SAE grade, depending on the engine.
For anything driven regularly and all year round, a true multigrade is the kinder choice.
Frequently asked questions
Is 20W-20 a monograde oil?
Formally no, in practice close to it: the gap between cold and operating viscosity is minimal. In everyday use it therefore behaves like an SAE 20 and not like a modern multigrade.
What do I use if my handbook states 20W-20?
Establish the present-day equivalent for your engine - for classics often 20W-50, for special applications a monograde as specified. A marque club or a workshop with experience of that engine is a more reliable source here than comparing numbers.
