Bob La Londe wrote:

For those who deride WD as a coolant / lubricant. It does wonders on
Aluminum. I know and have seen that I get faster results with the WD,
but some of my projects have cut times so long I can't stand there and
spray regardless. I just had never realized HOW MUCH difference it
makes. I am talking an order of magnitude difference. We aren't
talking a 20-50% improvement in efficiency, but in this particular
experiment nearly 2000%.

WD-40 works great with AL. The problem is that
it's flammable. Nobody wants their $100k CNC
mill to go up in a cloud of flame and smoke.