[Vadim T.]

My 2021 Z4 gave me a low coolant warning. I went to my dealership parts, gave them the car information and they sold me the blue coolant.

After I topped the car off, it hit me that the colors were different so I did some research and it looks like my car comes with HT12 and I am seeing mixed information on whether BMW blue coolant can be used to top off Green.

I have a flush scheduled for next week, but will probably be driving a few hundred miles between now and then. Do I need to cancel my trips and try to do an emergency flush or mixing the two formulations will not cause immediate harm?

Thanks!

P.S. When I called the dealership afterwards, they told me they actually top off fluids for free. Why I wasn't told that from the start... no idea! Now I have to go through this headacheinstead

[Brandoch]

If you need to top up, you have a leak. You should investigate the source of the leak.

[Vadim T.]

Originally Posted by Brandoch

If you need to top up, you have a leak. You should investigate the source of the leak.

Yes, I'll ask them to check that too. I had added 24oz... it wasn't a small top-up. My original question still stands through. Will my car turn into a pumpkin in a few hours of driving or I have a week before I take it in for service? Thanks

[alex2364]

BMW HT-12 can be used in any vehicle that currently contains G48 coolant (blue), but G48 should not continue to be used in vehicles that were originally filled with HT-12.

https://www.getbmwparts.com/oem-part...kgUGFnZQ%3D%3D

[Vadim T.]

Originally Posted by alex2364

BMW HT-12 can be used in any vehicle that currently contains G48 coolant (blue), but G48 should not continue to be used in vehicles that were originally filled with HT-12.

https://www.getbmwparts.com/oem-part...kgUGFnZQ%3D%3D

So I guess they aren't chemically incompatible or backwards mixing wouldn't be allowed either. More likely the HT-12 is better suited for newer vehicles. E.g. I should have a bit of time before this becomes an issue?

[pbonsalb]

Best price I found for HT-12 shipped — I just bought 4 gallons.
https://shop.valvolineglobal.com/pro...oSdD6l-WG3SKeN

[Vadim T.]

Originally Posted by pbonsalb

Best price I found for HT-12 shipped — I just bought 4 gallons.
https://shop.valvolineglobal.com/pro...oSdD6l-WG3SKeN

Is she leaking that bad??

[pbonsalb]

I bought 4 gallons because I do a fair amount of DIY work and like to have some on hand. Have 2-3 gallons of the blue coolant for my older BMWs, but was down to half a gallon of HT-12 that I already mixed 50/50 and have the F90 M5 on the lift now to change the thermostat. You would need probably 2 gallons of concentrate if you want to change your now mis-matched coolant, so you could buy less than than me — just draining the radiator and not using the block drains could be 1 gallon of concentrate mixed with 1 gallon of water (full capacity is more than 8 quarts). I agree with the comments that you should should fix any leaks as part of your work since 24 ounces is beyond what I would call a top off.

[RockCrusher]

I'll add that the few times I've had to add coolant and in an amount that could only mean a leak I used distilled water to bring the coolant level up.

I was ok with this as I don't live/drive in arctic cold weather conditions.

But the distilled water bought me some time during which I then set about searching for the leak.

[slilley]

OP, you are fine to drive the car as-is. There are probably thousands of BMWs driving around with a little bit of mis-matched coolant. Is it ideal? No. Will it do any harm in small-ish top-off amounts? Probably not. That's what I've decided after researching it, and making the same mistake as you on one of my other BMWs. Now I've got both coolant on hand.

As for the leak possibility, as long as you only needed to add a small amount (less than a cup), it's probably not a leak. I'm now in the habit of checking my coolant levels on all my cars every 15K miles, as I've now seen the levels dropping slowly on ALL my cars: BMWs (three), MINI (two), VW, and Porsche. Some cars will go 30K without needing a small top-off. But by 45K miles, every car I've owned for the last 15+ years has needed a top-off. Back in the day I'd flush the coolant every 2 or 3 years, so I suspect this was occurring back then, but I never noticed it because the coolant was being refreshed more frequently than a top-up was needed. My 15K interval to check the coolant levels is probably too conservative, but I'd rather check more frequently than have the low-coolant light go on at a time when I'm incapable of adding it.

As others have said, if you are in a pinch, simply add distilled water to bring the level back to full. The capacity of most cooling systems is a couple of gallons, so adding a cup or two of distilled water isn't going to change the concentration enough to make a huge difference.

[pbonsalb]

The OP wrote that he added 24 ounces of coolant.

[Vadim T.]

Originally Posted by slilley

OP, you are fine to drive the car as-is. There are probably thousands of BMWs driving around with a little bit of mis-matched coolant. Is it ideal? No. Will it do any harm in small-ish top-off amounts? Probably not. That's what I've decided after researching it, and making the same mistake as you on one of my other BMWs. Now I've got both coolant on hand.

As for the leak possibility, as long as you only needed to add a small amount (less than a cup), it's probably not a leak. I'm now in the habit of checking my coolant levels on all my cars every 15K miles, as I've now seen the levels dropping slowly on ALL my cars: BMWs (three), MINI (two), VW, and Porsche. Some cars will go 30K without needing a small top-off. But by 45K miles, every car I've owned for the last 15+ years has needed a top-off. Back in the day I'd flush the coolant every 2 or 3 years, so I suspect this was occurring back then, but I never noticed it because the coolant was being refreshed more frequently than a top-up was needed. My 15K interval to check the coolant levels is probably too conservative, but I'd rather check more frequently than have the low-coolant light go on at a time when I'm incapable of adding it.

As others have said, if you are in a pinch, simply add distilled water to bring the level back to full. The capacity of most cooling systems is a couple of gallons, so adding a cup or two of distilled water isn't going to change the concentration enough to make a huge difference.

Thank you!