This has nothing to do with this thread, but I just could not resist posting this!
Right you are caddy. I cannot help but wonder at this post. I mean if I was so desperate to change it before an oil change, I would pull the old, put my thumb over the hole, then work in the new. I cannot fathom losing more than a cup of oil.
Hey Tester, I’m not opposed to things that work and do no harm, but tell me, would your shop vac have a what 10+ft hose on it or do you shove the vac under the hood and then go up on the lift…AND…Does the vac do a sort of Bong Rip Bubble on the oil or what? Or Does the oil just hold there kinda like a “Stargate portal” affect…lol Curious…on several levels. Also how many x would you have to do this? I mean I’ve never messed up one single drain bolt in my life…fixed maybe 5?
This is just about the dumbest idea I’ve ever heard. If one WERE to try to save the old oil, a far better way to do so would be to drain it into a clean pan and then pour it back in after. But I have to tell you that in my opinion saving the old oil is about the dumbest thing I’ve ever heard.
I’m urious, if he’s (whoever “he” is) having you save and reintroduce the old oil, how’s he having you change the drain plug? Is he having you install a rubber expansion plug (a “boat plug”) instead of correcting a plug problem PROPERLY??? Or is this whole thing a joke?
MB- I was wondering the same thing. Why no just drain into a clean pan. Why would anyone do it any other way.
As for pouring the old oil back in…well I agree in this case it’s probably just best to put new oil in…but when I lived in Messena NY for a few weeks we would drain the oil on our car every night and bring it inside when temps dropped below -20. Then pour it back in the next morning.
Ouch! Yesterday I changed my oil in temperatures in the 30’s. It was downright chilly. I can only imagine the pain of doing it every day in sub-zero temps! You’re a tougher man than I!
I was 21 at the time. Was doing a research project for college. We lived in an apartment and had no access to electricity for a block heater. One night it hit -40…And synthetic oil wasn’t readily available.
I tip my hat to you. BRRRRRRRRRRRRRRR!!!
I said the same thing as you guys did…way up early in this post…Drain to a clean pan…do the job…pour the oil back in IF you must reuse it…say if it was just poured into the engine…no need to waste good oil…a clean drain pan is all you need…no vacuums no doo dads…nada…
And I have to say that I’m shocked at Mr level headed damn near always correct TESTER…doing this…LOL…I’m the one who is supposed to come up with the nutty ideas that work, but are a little “off” I do funny things all the time and this method isn’t THAT screwy, really…its just a little strange because I think many or most of us would just use a clean pan…cant tell you how many X I have drained oil into a purposely cleaned oil drain pan knowing that I would use it again…I didn’t think that was much to “go through” to re-use the oil…it was just what had to be done…If the vac works, I think its kinda cool…but in an unnecessary way.
Blackbird
I wasn’t the only one who did it…Just about everyone in the apartment did it. If not you’d never be able to start your car in the morning…and if you did the oil would be like molasses and probably destroy the engine in short order. Good thing it was only for a few weeks.
Mike, its a good theft deterrent as well, you know the cars are not going far if someone tried to steal it… lol
PS where is that guys post from a few weeks ago with a DSL van in NYC with no block heater, NEW IDEA !! 
Tester always has a decent and usable comment and it sounds like he runs his own shop (or at least works in one). I’m going to retract my earlier skeptical comment and believe that there must be a reason to hold a vacuum in an engine while removing an oil plug. Me, myself . . . I’m not a mechanic by profession and can’t see why a simple drain and re-fill wouldn’t be easier, but some mechanics obviously perform this procedure. So to answer the OP . . . I think that you got a bunch of opinions on both sides of the issue to tell your shop manager about. Some folks pull the vacuum and remove the plug and some folks remove the plug, drain the oil, install the new plug and re-fill. Rocketman
Performing a task that sucks.
Tester
The only possible reson I could see to vacuum the oil out would be if the plug were somehow seized into the hole and needed to be drilled out. I’ve never seen or heard of this happening, and cannot for the life of me see how it would be possible, but in the event that it did happen I suppose vacuuming the oil out would make sense.
The oil isn’t being sucked out. The vacuum applies a negative pressure in the crankcase so when the drain plug is removed the oil doesn’t drain out.
I do this when someone has their oil changed and afterwards oil leaks from the drain plug because either the gasket washer is worn and won’t seal, the gasket washer is cracked from overtightening the drain plug, or the gasket washer is missing. So instead draining the oil in order to replace the gasket washer and charge the owner for an oil change, I use the vacuum to prevent the fresh oil from draining and can swap out the gasket washer in ten minutes, and I do this for free as a good will gesture.
Tester
I dunno. I see your point, but still feel it’s easier to just drain and refill the oil, even if one uses the same oil and a clean drain pan.