Why are car fluid suction pumps not popular with mechanics (for oil changes) and would you recommend them for home mechanics?

Question

They seem like a great idea to me and if the oil is cold it's unlikely to melt the plastic tubing allowing anything to fall in. It seems like an effective method to do oil changes so why aren't they used by garages?

Also what's the worse that can happen if a something falls in there, I imagine the dipstick channel goes to the sump, so in worse case if on the rare occasion you mess up you just have to remove the sump, clear and put it together again?

Many home mechanics do not feel comfortable going under the car, would you recommend it for home mechanics?

Answer 1

Well, there are a few of reasons I can think of ...

1. Gravity just works better. You can get more oil out of the sump using gravity than you can with a pump. Albeit, in some cases what's left by the pump may be negligible.
2. Gravity is easier. You just let it do its work. Pull the plug and let physics do its thing.
3. Gravity doesn't take as long. You don't have to stand there and keep working the pump, which frees you up to do other things, like prep the new oil filter.
4. You don't have to purchase an extra item (the pump) to make things happen. You still have to have some container to keep the old oil in until you use the new oil (and thus have an empty container).

Most garages will have lifts, which makes getting to the oil plug all the more easy.

If one of your arguments for using a suction pump is that you don't have to jack up the car by using one, most cars' oil filters are located underneath, so you have to jack it up, put the pan under there to catch any dripping oil, then crawl under and remove/replace the oil filter.

As for your last question, depending on what it is, if you have part of the drain tube drop down into the sump, you can possibly get it out through the drain plug hole, but worst case, you have to pull the oil pan (sump) in order to retrieve it. I wouldn't want that left in my sump. And think of the time it takes to pull the sump? When you're talking time, you're talking money. Not wasting either is quintessential to operating a prosperous business.

Don't get me wrong, some people swear by using a suction pump to get the oil out. In some cars it's just easier to use one all around, due to their being shrouding underneath the vehicle which has to be removed. There are reasons to use one. Most shops just aren't going to spend the time/money to get/use one when they really aren't more efficient than just using gravity to do its thing.

Answer 2

I'm not sure why you say they aren't used by garages. I'm aware of at least one Volkswagen Master Tech who swears by them and uses them for oil changes frequently. It can be quicker than removing the undertrays from some modern cars.

A note about oil temperature though, they work best with oil that's been warmed up and this can be drawn up with less effort.

Answer 3

On most engines, going through the dipstick tube would be the only way to reach the bottom of the pan from above. Given the size of most dipstick tubes, you would need a very small hose to fit through it which would require more time and energy to pump the oil out vs. just removing the drain plug.

Now if you were to fit a larger diameter hose around the tube, you would start sucking air long before the pan was empty.

Then most of all, why risk having something break off in the engine requiring a removal of the oil pan to get it out?