2007 Subaru Outback - mixing antifreeze

I have a 2007 Subaru outback/ standard transition. We are hitting freezing Temps and my coolant has a real light tint of green to it. Can I mix the peak antifreeze 50/50 blue color to what’s already in my radiator?

You should use the anti-freeze that Subaru recommends.


Subarus are more prone to cooling system (head gasket) problems than most brands. It’s wise to service the cooling system by the book, including change intervals and coolant specs.

Safest to have it flushed and refilled with what Subaru currently recommends for your model (it will be their brand, of course) - this is for materials compatibility reasons (metals, head gaskets, cooling system plastics, etc.). Then follow Subaru’s recommendations for change intervals, it’s important.

Be cautious with aftermarket coolants, some probably are okay but others not - it depends on details of their individual chemistries. Color isn’t standardized between brands and some chemistries shouldn’t be mixed, so flush until clear.

My parents’ 2006 Outback (6cyl. engine) was maintained for years by an independent shop who used Peak Global (this is the amber version for cars, not the red version for trucks, which differs in some ways). When we took over the car in 2017 I checked with Peak (Old World Industrties), who at that time (and maybe still) supplied Subaru’s AF and was told that Peak Global and Subaru’s extended life version were fundamentally the same chemistry. We’ve changed the Global once since then and all is well, so far.

If you see any hint of cloudiness in your coolant, then it is time to drain and refill. Use the recommended anti-freeze and if you DIY, you NEED this kit to get all the air out.