Coolant mix

[Kilzon]

I’m curious if it’s ok to mix original Subaru coolant and “Aisin” blue coolant. They are both blue but idk if it’s fine to mix them since they are different brand. (Car is filled with Aisin and I just need to top my reserve tank.  I have some original Subaru coolant) 

[KZJonny]

I wouldn’t worry about mixing the two blue coolants together.

As far as I know, the colour indicates the type of coolant; it’s ‘chemistry’ so to speak. Eg, all blue coolants should be the same/similar, likewise all ‘red’ coolants should be similar, and mixable.

Sometimes fluid types are super important, like atf in Subaru automatics. (Use only Subaru or Idemitsu HP!!!) others are not so much.

Start a discussion about oil if you really want to stir people up. 

[kzr750r1]

Did subaru change to blue in the later versions? I've always used the long life Green fluid from Subaru.

Good point on the AT fluid.

[Max Capacity]

My Subarus have always been on green coolant, normally I use Prestone. Read the info on the blue and green Prestone. Maybe I'm missing something, but the green seems fine for all cars. If you buy the concentrate also buy DI water. It's $1.16 a gallon at Walmart. 

Even the 2018 3.6R has green coolant in it from Subaru, owners manual say's it's good for 11 years.

[KZJonny]

Maybe it's regional? I don't *really* remember what was in my '02 Outback, but I think it was blue.

Both of my '05s have always had blue fluid.

I sincerely doubt it makes much of a differerence at this point. There isn't a car being made in the world any longer where the coolant doesn't touch aluminium. Probably iron in the mix somewhere as well. The protective additive packages are no doubt better than they used to be, but I think a well flushed system attached to a rad that hasn't corroded away, and is refilled with clean fluid of any colour is going to be fine. The days of the harsher additives that were designed mainly to keep iron blocks from rusting but that caused some problem with aluminium are long gone.

[KZJonny]

On 10/14/2022 at 9:27 AM, Max Capacity said:

 If you buy the concentrate also buy DI water. It's $1.16 a gallon at Walmart.

If you happen to have a dehumidifier in your house, it also produces distilled (deionozed water) for free.

Not exactly a big cost savings, but if you’ve got one, it may just save a trip to the store at least.

[NORULZleggy]

Amsoil coolant for the WIN!  It aint cheap.