Oil change by vacuum

[Pbondar]

Since there is no dipstick on a B58 engine is this a moot / irrelevant point?

[R60BBA]

I don’t know whether this is true, but I have heard that you can never get all of the oil out of the engine by sucking it out from a vacuum extractor.

Especially on cars with baffled sumps, which means that you are unable to get the “dregs” at the bottom (which is the part of the oil which you most want to flush out of your engine during an oil change) hence why it is more preferable to drain from the sump plug...

Here are the motivations that I like to use vacuum. Glad to have more discussion:
1. I have done an experiment before on my Audi. I have drained under the car until the oil doesn't drip out. Then I immediately apply vaccum from above. It turns out that there is a ~0.1 L of oil residual extracted by vaccum. Maybe this problem is specific to the configuration of sump(?). Not sure G29 is the case.
2. Consider Stoke's law, the velocity of sedimentation of particle is inversely proportional to the square of particle size. For fine debris, it's practically difficult to wait until all debris settle. So my idea is to suck them when they are suspended in oil, and that I do vaccum on a hot engine. The debris / sludge alternatively suspend and circulate in hot oil.
3. Also similar to 1 & 2 above, there is always oil remains in the car. You can never drain / vacuum all of them out.
4. I do oil change whenever I feel that the car does not run smooth as if I just complete oil change. In general, I change it in 2500 ~ 3000 km (probably due to my driving habit). Given this frequency, I prefer a quick job of vacuum.
5. When I go to the dealer in every 10,000 km, they will help me to drain from bottom. So it's 3 to 4 vaccum then 1 drain.

As you said I think it depends on the engine and in particular the design of the sump.

Some of the newer cars don’t have a drain plug and so the only way to take out the oil is via a vacuum.

I am also hearing that this is the preferred method for main dealers, even on cars with sump plugs. However I am also hearing that it is preferred because it is faster and BMW main dealers are only giving their technicians 9 mins to do the oil changes.

I’m not sure if you are aware but quite a few of the people who I know that have worked at various main dealers in the UK have confirmed that in essence technicians get points (which translates into £££) for doing jobs as quickly as possible, yet there are no bonus points for being super thorough etc - which in turn creates an incentive culture whereby techs often ‘cut corners’ to do jobs as quickly as possible for bigger bonuses.

Yes you are correct in that you will never get all of the oil out of the engine upon an oil change, but for a car with a baffled sump the preferred method is to drop from the drain plug.

Perhaps you should try the test you did on your Audi to your Z4?...

[R60BBA]

Out of curiosity I decided to Google this and found this video.

It basically confirms what I was saying above:

[Chris_D]

When I started using my PELA pump I was surprised to find that ai was removing more oil than by previously draining via the sump. I made a post about it after sucking out 7.5l, where I should have been removing 6.5l or less by using an extra step of going back the following morning to to suck out any residual oil that had drained down into the sump overnight.
It’s now my own preferred method.

viewtopic.php?f=2&t=111405&p=1608746&hi ... p#p1608746

Maybe you could tap a hole into the side of the sump and make your own dipstick tube?
Yw

FDB2555D-39D2-4DE4-AFB7-22B8875942D7.jpeg (112.67 KiB) Viewed 545 times

[enuff_zed]

Since there is no dipstick on a B58 engine is this a moot / irrelevant point?

Apart from the one behind the wheel.

[Mister T]

But a lot of garages don’t just drain the oil they flush it through which ensures you get all of the old oil and any debris out of the sump. So I don’t think your argument works.

They genuinely don't, unless you specifically ask/pay for it.

[srhutch]

But a lot of garages don’t just drain the oil they flush it through which ensures you get all of the old oil and any debris out of the sump. So I don’t think your argument works.

They genuinely don't, unless you specifically ask/pay for it.

BMW advise that you DO NOT carry out engine flushing.

[SiJar]

Oh ok thanks, I learn something new each day