I am going to replace the valve cover gaskets on my '03 Legacy with 110k on  the clock, oil is leaking into spark plug holes.  Might as well put new plugs and wires in while I am in there.  Are NGK double Platinum factory.  Cause I kind of remember NGK copper being in there factory?  Been LONG time since had factory plugs in it.  Also should I get good after market wires or stck with OEM?

You can use NGK or Denso wires if you like.

I think double platinums are recommended for that engine but I'm not 100% sure. If you have the owners manual it will say in there.

The wasted spark system on subarus will cause platinum plugs to fair very quickly. When I did the head gaskets on my mom's 04 outback last summer I didn't notice that the parts store had sold my nephew the platinum ngks instead of the standard copper v powers. Well 7k miles later she had horrible misfires and the car was barely drivable. Throwing cels for cyl misfire on all but one cyl. Fresh set of ngk v powers and all is well.

 

Had to break out the owners manual to get the correct plugs btw, advance auto's computer did not have them listed properly.

Edited March 19, 201511 yr by 86BRATMAN

The Double platinum plug (not to be confused with a Bosch platinum + 2) is designed specifically for waste spark systems. Platinum on both the center and ground electrodes prevents the wear that causes misfire problems in waste spark systems.

The 05 Outback non-turbo 2.5 uses NGK double platinum FP5AP-11.

The owners manual in the 04 listed 3 different plug types NGK BKR6E-11, NGK BRK5E-11 and another non ngk plug for the ej25. None of which were platinum anything plugs. I can provide pictures of said owners manual Friday if need be.

86 Bratman you are correct just pulled out manual all are copper NGK's or a copper Champion?  Would Iridium be worth the money to put in? 

I would run the NGK plugs over Champions, just as a matter of past experience with both brands. I would stick with the copper plugs.

Always NGKs in Japanese cars.  Copper because of performance benefits, I would think since replacing tem is such a task.  Something like Iridium's with a longer service life would be worth it?