OT: You suck the oil out of where?

[whiskychaser]

An interesting discussion about removing engine oil by vacuum rather than via the sump plug:
http://www.honestjohn.co.uk/forum/post/index.htm?t=81725
There seem to be some strongly held views. While the insults traded are not of the Black Adder standard they are not bad. My own favourite:
'You poor misguided soul - you'll only have yourself to blame when the sump falls off, the brake hoses burst, your radiator springs a leak, your hair falls out and your Yorkshire puddings don't rise':D

[Tiger]

I use this...

It works perfect and powerful as you are using your air compressor to creat vacuum.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=46149

[Ferret]

It's amazing how internet arguments about this stuff can cause such riots :)

[ss2115]

Its very common to suck the oil out on bigger inboard boat engines.
Often you just cannot get underneath, but even if you can its usually preferred to suck out to avoid any oil spillage in the bilge.

Crud floats and will drain or suck out mostly.
Sludge sits at the bottom like mud and even draining by gravity via a sump plug doesn't automatically get rid of it.

Its why engine flushes became popular for a while, but then faded away as residue remained and diluted the new oil. Not good for the big end or main bearings.

[Ross]

Aside the boat/bilge use I maintain these are toys for folks unwilling to soil their hands.
The drain plugs are in the bottom of the sump where any debris will be. Drain plugs are often magnetic, routine inspection can catch problems early. Being under the car provides an opportunity for inspection. Often the oil filter is underneath anyway.
Dipstick tubes usually terminate elsewhere leaving more dirty oil behind if you extract from there.
I can't think of a good reason to use them other than stated above.