Best Coolant for CNC Milling Machine and Lathe for small shops
I've been using KoolRite 2290 coolant in the Tormach PCNC 1100 milling machine for years. A 5-gallon bucket has lasted almost 10 years. Even though it says that it resists bacterial growth, it can get pretty nasty if it sits for a while. Using an air bubbler (tube with holes in it, because the stones always end up clogging) and a skimmer or oil absorbant pads helps to prevent bacteria growth. The air bubbler works best to prevent anaerobic bacterial growth but allows it to evaporate faster.
So, I'm searching for something better.
TRIM 690XT seems to be well-liked, but some say it has a strong smell. https://www.practicalmachinist.com/forum/threads/trim-690xt-smell.374761/
Fuch's ECOCOOL 7830 C appears to be really good, low smell. I contacted Fuchs Lubricants USA and they sell direct and offer 5-gallon pails as the smallest amount (costs close to $400 in 2023). They did offer a sample pail for testing before committing to a larger amount.