. Coolant is a major part of this, so I have been doing some research.
Firstly, modern Anti-Freeze is not like the old stuff. It contains corrosion inhibitors. Make sure you use it in the summer too, and don't be stingy with it. 40-50% AF in your coolant is about right to keep your waterways clean (& make your pump/stat/rad last longer).
The old winter-only stuff was methanol based. This is the stuff which does not contain any corrosion inhibitors. If you can find any of this, avoid it.
For years the standard has been Ethylene Glycol. The 'standard stuff' is usually blue or green and contains inorganic silicate-based (MEG) corrosion inhibitors. This requires changing every 2 years because the inhibitors get used up.
Around the turn of the century, "Organic Acid Technology" (MEG with OAT) corrosion inhibitors became available. Anti-Freeze with this supposedly lasts for up to 5 years and runs cleaner than the standard MEG stuff. MEG with OAT anti-freeze is usually red or pink. OAT anti-freeze should only be used with Aluminium radiators because it reacts with copper & brass. In cases where this can be used, it runs cleaner the blue/green stuff.
Mixing the two shortens the life of the corrosion inhibitor.
There is no guarantee that all blue/green antifreeze has silicate corrosion inhibitors and all red/pink has OAT. Check carefully first.
If in doubt, use silicate at about 50% concentration, renewed at least every 2 years. Don't go too high with the concentration because water is better at carrying the heat away.
Don't assume that because it is not red then it is not organic. Check first.
Clicky
- NOT. 
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