It's called Subaru "Professional Use" Cooling System Conditioner, in a blue 4 oz. bottle with a red cap. The bottle is stamped "Holts" at the bottom.

Some other forums say that this is the same as Holts "Radweld." Check out the link here:  

http://www.gtcars.ca/online/subaru-mailing-list/68996-subaru-coolant-conditioner.html

Ed
 
>  From all accounts,  I guess Subaru engines can have leaks like WBX'ers
> 
> Anyone know the official name of the stuff Subaru  uses to add to
> coolant to stop leaks?
> 
> Will it work for WBX engines - particularly for head leaks.
> 
> Thanks
> 
> John Rodgers
> 88 GL Driver
                                          
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