[EQUANT]

Hi guys,

I have some OE BMW coolant around and it says on the bottle that a 50:50 mixture will give you a -40*C freeze point, so i decided to test it out.

I poured in a small recipient equal amounts of antifreeze and water and then tested the mixture. It said -18*C!

I repeated the process, put same amount of antifreeze, but half the amount of water - and it reads -25*C!

I don't understand, what's wrong?! How do i get it to read below -30*C?
I used the same tester to test a fresh mixture of antifreeze on another car (Peugeot 207) and it reads precisely -37*C, as it should.

I tested the bmw antifreeze alone and the tester goes off the scale, so it's concentrated, not pre-diluted.

Any thoughts?

[N8N]

if you are using an old ball tester it is calibrated only for ethylene glycol type coolants. I don't know what the BMW coolant is but it may be propylene glycol, OAT, etc.

The tester works by reading the specific gravity (density) of the coolant/water mixture and it is ASSuming that you are using a mixture of EG and clean water - but the SG vs. freezing point graph will look different for different types of coolants.

[EQUANT]

Here is the label on the BMW antifreeze and a picture of my tester. Antifreeze has ethylene-glycol and the tester says it's good for Ethylene-glycol.
Any other thoughts? winter is coming and i'm not comfortable with ~ -18*C that it's indicated with the current antifreeze, as temps may go below that.

[Reznick]

I was under the impression that the anti freeze bought from BMW was straight antifreeze and had to be mixed with water to get 50/50. If you go to pep boys and look and anti freeze you'll see some bottles marked 50/50. We buy it by the 55 gallon drum so I'm use to adding water myself

[John 070]

Maybe times have changed, but a 50:50 mix is good to -34F, not C. And if you go beyond 70% antifreeze, you actually reduce the anti-freeze and anti-boil. Who the heck knows, I was always better at physics than chemistry.

[EQUANT]

This antifreeze has to be mixed with water, 50:50, as specified on the bottle. The weird thing is that 50:50 mixture only has a ~ -18*C freeze point, which is not enough.

@John - you are right. As i said, in the Peugeot they put pre-diluted Peugeot antifreeze and measured it with the same tester and the result was: ~ -37*C (-34*F -ish).

I don't know how to get the BMW antifreeze to the same point. I will probably go to BMW and ask them to check the coolant freeze point and replace it, if necessary (although it had just been replaced at a local indy)