So, my new to me 05 Legacy 2.5 owners manual says when changing the antifreeze, to add bottle of Subaru brand "conditioner"

Is this a stealership euphemism for "can I have some more of your money please", or does it actually serve a purpose?

All the other vehicles I've ever owned just say to put new stuff in. What gives?

Do a search here about headgasket, the Phase II motor had an external leak issue (more of a seeping problem) that was cover for the years 2000 to 2003 I'm not sure why the 05 manual says you need it but I'd check with the dealship and see if they can explain why it's needed. Maybe it's a water pump lubricant? As far as I know the leak problem was coreected in 04.

The conditioner is Holts Radweld from the U.K. with a Subaru label on it. It's only like $1.50 but some dealers charge $5 or more.

 

There's a TSB to add the conditioner on some older models. I guess Subaru decided the best "fix" was to just put that in the manual and not actually fix the problem.