I have been using the Shell Dromus B http://www.epc.shell.com/Docs/GPCDOC...S_Dromus_B.pdf for decades. Actually I first used it over fifty years ago when I was just an apprentice.
My shop does mostly aluminum and leaded steel with some mild steel and we have found boosting the concentration to 10% or even a bit higher gives better results in tapping.
This coolant washes off the aluminum just with a hot (85 degree) water spray and leaves no residue that causes problems when anodizing aluminum and it does not affect (cast) acrylic or polycarbonate. This is why I am very reluctant to ever try a different coolant.
Before we started using the Keller units it would get quite grungy with tramp oil and when the machines were not in use would get a rancid smell. Now that we have controlled the tramp oil it is fine and we rarely clean out a machine to replace used coolant. Most of our machines make lots of chips and the carry-out with the chips means the coolant is being replaced.
An open mind is a virtue...so long as all the common sense has not leaked out.