can i switch to 0W-20 in my EJ25?

since i also have a '12 impreza that uses 0W-20 it would make things easier for me if both cars use the same oil. i think i read something about 5W-20 shearing down to 0W anyway or something like that.

If the engine is specified for a certain oil weight you shall never go below what's specified to the right of the "W".

 

If it's rated for 5W30 then you can go 0W30, 10W30, 0W40, 10W40 etc. but not 0W20.

 

The reason is that the figure before the W is how thick the oil is at low temperatures while the figure after the W is how thick the oil is at high (working) temperatures.

 

So a 0W will make cold starts easier than a 10W oil, but at the other end of the range a 20 oil is thinner than a 30 oil and may cause wear and even damage on the engine because it's not designed for it.

i was thinking it was 5w-20, i decided ill just stick with the 5w30

Same problem, 5W20 won't be good for an engine specifying 5W30.