OEM Subaru Radiator Caps

Subaru engines use two DIFFERENT radiator caps. One cap (the one with the ears) has a valve in it that allows the upper coolant reservoir to draw coolant into itself. The other cap (the round one with no ears) does NOT have that valve in it. If you put the cap with the ears on your radiator, your coolant reservoir is not going to work correctly.

The cap with the ears goes on the coolant expansion tank. The round cap with no ears goes on the radiator.