Cold weather making my coolant look low… is this normal?

General Discussions and Questions
1

Got a brand new 2025 Outback in November. The other day I was refilling the washer fluid and noticed the coolant in the reservoir was way down near the ‘low’ mark. It was early morning, about 35°F outside. Took it to the dealer, they topped it off, and when I checked later (after driving ~12 miles in 50°F weather), it was sitting an inch above ‘Full.’

This morning was colder, around 18°F, and I checked again—it was right back down to the ‘low’ mark. After some driving (~25°F outside), it went up again, sitting just above ‘low’ when hot.

Car runs totally fine—no overheating, temp gauge holds steady at 195-200°F, heat works great, and I don’t see any leaks. Under the hood is spotless since it’s new. I did hear some sloshing before the dealer topped it off, but that’s gone now.

Is this something to worry about? Anyone else in cold areas notice their coolant looking super low in the morning?

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2

Yeah, I think we all shrink a little in the cold haha.

3

Cypress said:
Yeah, I think we all shrink a little in the cold haha.

I was in the pool!

4

Totally normal. Coolant levels change a lot with temperature. As long as you’re not losing fluid and it comes back up when warm, you’re good.

5

Nothing to worry about.

6

The level in that tank isn’t super important—it’s just the overflow for the radiator. As pressure builds, coolant moves into it, and when it cools down, it pulls coolant back into the system.

7

Jacob said:
The level in that tank isn’t super important—it’s just the overflow for the radiator. As pressure builds, coolant moves into it, and when it cools down, it pulls coolant back into the system.

Yeah, that makes sense. Just caught me off guard seeing it so low in the morning. Figured a new car wouldn’t have any coolant loss, so it seemed odd.

8

@Adley
You probably haven’t lost any at all—it’s just sitting in the radiator. If you’re worried, check under the radiator cap when it’s cold and see if it’s full.

9

@Adley
Just so you know, when your engine is cold, the coolant should be near the ‘low’ mark. When it’s warm, it should be up near ‘Full.’

10

Sidney said:
@Adley
Just so you know, when your engine is cold, the coolant should be near the ‘low’ mark. When it’s warm, it should be up near ‘Full.’

Huh, my owner’s manual actually says it should be at ‘Full’ when cold. Now I’m confused.

11

Sounds like the whole engine needs to come out. Maybe twice, just to be sure.

12

Ezra said:
Sounds like the whole engine needs to come out. Maybe twice, just to be sure.

Third time’s the charm! Like the candy. And if you’ve got Charms in the car, you’re gonna have a bad time.

13

If mine ever gets that low, I top it off. Better to have a little extra than risk it sucking in air.

14

I tell customers this all the time—coolant will slowly evaporate from the overflow, especially in cold weather. Just don’t let it get empty.

15

That reservoir exists for a reason—it’s there to handle coolant expanding and contracting with temperature changes. When the engine is cold, it pulls coolant in. When it’s hot, excess fluid moves into the reservoir.

16

Noticed the same thing in mine. Grabbed some Subaru Super Coolant and added about 6oz. No big deal.

17

I have to top mine off now and then too. Never had to do this with other cars (first Subaru). Noticed the tube just sits in the tank, so maybe some is evaporating?

18

Fluids expand and contract with temperature changes. Coolant is no different.

19

That tank always makes it look lower than it is. When full, it’s actually a couple inches from the top. Subaru really could have designed that better.

20

If you’re really worried, you can add a little distilled water before starting it up. Won’t hurt anything.