Minor threadjack with a question here. Once you pull a vacuum deep enough to boil water at the ambient temperature, how much additional value is there in pulling down to a small number of microns? I understand that removing all the air/water from the system eliminates some dead load from the compressor which increases efficiency. But practically speaking, is there any difference between achieving 29.5" and an essentially perfect vacuum?

I have Mastercool single stage wet vane pump which doesn't pull down nearly as far as a two stage pump. Best I can recall it's rated at 100 microns, whereas the two stage pumps are rated at 25 microns. In the real world, is one of these really better than the other?

I haven't actually had to perform an a/c repair in 5+ years, knock on wood...

- JimY