How low of a vacuum should we pull on a system?

JB recommends that a system be pulled to at least 250 microns and held at least five minutes. On any polyester oils in a system, it is recommended to pull a much lower vacuum as moisture is very difficult to remove even with heat and vacuum.

vacuum leak detector 

question for vacuum pump and vacuum gauge

IMPORTANT- Always check the oil level with the vacuum pump running

Why do I need to check the oil level when the pump is running?

How low of a vacuum should we pull on a system?

Can I mount my micron gauge onto the vacuum pump?

I am able to pull a vacuum on my system, but when I blank-off, the micron gauge rises rapidly.