All About SUBARU Cooling System Conditioner SOA635071

Today we'll discuss all facets of the SUBARU cooling system conditioner, what it is, how to use it, why it is necessary, who produces it, where to buy it, and more.

What is the SUBARU Cooling System Conditioner?

The SUBARU cooling system conditioner is a product intended to be added to the engine coolant when it is changed.  We have photos here.

What SUBARU vehicles require the cooling system conditioner?

Certain model SUBARU vehicles were listed in SUBARU bulletin WWP-99 were supposed to have the conditioner added.  Namely these included the following SUBARU vehicles (within a certain VIN range):

  • 2000-2002 MY Subaru Legacy and Outback with 2.5L engine.
  • 1999-2002 MY Impreza with 2.5L engine.
  • 1999-2002 MY Forester with 2.5L engine.

The specific VIN ranges are as listed below:


Model  FromTo
  Outback WagonY*600001Y*674127
  Outback Wagon1*6000011*679753
  Outback Wagon2*6000012*605593


Can I use the SUBARU cooling system conditioner even if my SUBARU isn't in the list above?

It would appear the answer is yes.  An SUBARU cooling system article titled "Cooling System Overview" from May 2005, in a section discussing Genuine Subaru Cooling System Conditioner (Part Number SOA345001) added, stated:

You, too, should be using it every time you drain and refill a Subaru cooling system. Fuji doesn’t approve of any aftermarket additive whatsoever, so why argue? Take four ounces of coolant out of the radiator, shake the bottle, then pour the contents directly into the radiator filler neck, not the overflow jug.

Moreover, SUBARU TSB 09-47-07 titled "Cooling System - Coolant Flushing Machines and Additives" stated:

Whenever the coolant is changed, you must add Genuine Subaru Cooling System Conditioner. Genuine Subaru Cooling System Conditioner has been tested and approved for aluminum engines and radiators. 

Now the caveat would be the statement might be valid only for SUBARU vehicles that used the traditional SUBARU coolant.   SUBARU vehicles starting around 2008-2009 started using the blue SUBARU super coolant.

What is in the SUBARU cooling system conditioner?

SUBARU coolant conditioner ingredients listAccording to the product label, it contains a proprietary resin solution, borax decahydrate, and linseed meal.  I believe the linseed meal is what can be seen as the chunks in the product.  Similar products use ingredients such as ginger.

Who manufactures the SUBARU cooling system conditioner?

The bottle label states "Manufactured in England for Subaru of America, Inc.".  However, even the casual observer cannot miss the "Holts" embossed on the blue plastic bottle.  So it would appear the SUBARU cooling system conditioner may be manufactured by Holts in the UK.  Holts makes a product called Radweld.  The Radweld bottle bears a striking resemblance to the SUBARU cooling system conditioner bottle (except for the label).  See the comparison below:

Comparison of SUBARU coolant conditioner to Holts Radweld

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