Antifreeze

[SMOKEU]

Is it bad to mix different brands of coolant together?

[onearmedbandit]

I'm not sure myself Chris, but it isn't too hard to flush your system and replace the water/antifreeze. Just remember to bleed the system.

[neels]

Potentially, depending on their chemical components, particularly the anti-corrosion stuff they have in them.

Besides, if you don't know how long it's been in there it's probably not a bad idea to drain it and put some new stuff in. I can say this 'cos I get it free from work

[SMOKEU]

Will it damage an engine or reduce cooling efficiency if I add too high a ratio of antifreeze : water?

[steve_t]

All engines require antifreeze in the coolant for freeze protection, lubrication and corrosion prevention. The usual mixture is 50 percent antifreeze and 50 percent water. Once the concentration of antifreeze is greater than about 60 percent, the freeze point starts going back up instead of down. When the concentration gets too high, the silicates in the antifreeze can start to separate and form a thick gel that clogs radiator passages.

I'd imagine the same but opposite will occur for the boiling point and probably the ability to transfer heat.

[Flip]

There are few liquids better for transferring heat than water, it has a high specific heat and has a low viscosity. Problem is it freezes, boils and causes corrosion. Ethylene Glycol does not have as good heat capacity and is thicker, but has a higher boiling and lower freezing point.

All the std antifreezes are mixable, they comply with SAE and Din standards the same as oils. Don't know if I completely trust the cheap non brand stuff you can buy.

I do not believe a little too strong will be a problem, after all you usually top up with tap water. Don't most makers recommend 1:2 to 1:1 ratio depending on the freezing point required.

I use a 1:4 ratio in one car because it only needs a little corrosion protection and 1:1 in the landrover because it is driven into the high country in winter. I have owned the first car for 20+ years, its been raced and gone everywhere, its never had a cooling or corrosion problem.