Any disadvantages to running a vaccuum pump? (for oil)

Cudafever said

I'm not arguing with this at all.......just learning......
So the reading on the oil pressure gauge goes down when crank case pressure turns to a Vac.........Does that mean, that if you had high crank case pressure.....say in a boosted situation, with bad rings blowing into the crank case(no vac system installed). That the oil pressure gauge would read higher at that moment.

When the pressure gauge goes down under crank case vac.......how much does the gauge read...less.......a pound? 10? More???

Click to expand...

Yes, excessive crankcase pressure would make for a higher reading. But the higher the crank pressure, the more oil is going to be blowing out of the seals, pcv, breathers, etc.

The lower reading caused by crank vac will depend on the actual crank vacuum. 30" (hg) of vac is good for about 15psi, so 10" of vac would lower the reading by about 5psi.

The entire crankcase is at the same vacuum, so the oil pickup sees vac and so do the oil clearances, so the pump is still 'adding' the same pressure between the sump and the clearances. Now, if an engine is somehow very very heavily baffled, there could be a difference in the vac reading in the valve covers versus the sump, but it wouldn't be much - maybe a couple inches of vac.