Sucking oil out f sump

When changing engine oil, I've always drained the old oil by the old fashioned method of removing the sump plug.
However, I'm aware that some 'quick oil change' places (and may be
others) suck the old oil out using a pipe into the dip stick hole/tube. Plus, the early Smart Cars (the 450's) didn't have a sump plug (although a mod was available), and the standard service method was to suck the oil out. The 451's, at least the later ones, do have a plug.
While crawling under the Ducato this morning to change the oil, I got wondering about the pros and cons of sucking the oil out by the dipstick hole/tube.
One obvious con is the need for the kit, a pro is (presumably) speed and lack of mess. Plus, in some cases, you may be able to avoid having to even put the vehicle on a ramp etc, assuming you can access the filter from above.
I also think sucking may leave some 'sludge' in the sump. I tend to change my oil regularly- before the mileage at least, although only once per year (as specified- I don't cover the corresponding number of miles). However, if you do cover the max number of miles, or don't change the oil regularly, then sludge is likely.
Does anyone have experience of sucking the oil out? I'm not really thinking of changing how I change my oil, I only do a few changes per year and it is hardly a major chore, I'm just curious.
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On 10/07/2018 14:45, Brian Reay wrote:

Sludge was a "feature" in the old days when first I started rebuilding engines. My impression is that modern detergent oils keep debris suspended much better (based on the lack of deposits on sump plugs, when removed).
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On 10/07/2018 22:11, newshound wrote:

Toyota had a lot of problems with sludge in the late 1990's to mid 2000's, mainly I think on Eastern side of USA. Just a bit too cool in winter and standing traffic in major conurbations.
https://www.toyoland.com/sludge.html
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On 10/07/2018 22:11, newshound wrote:

Plus modern cars seem to use 'thinner' oil.
20-50 was, as I recall, the 'standard' in the 60s/70s etc whereas now 5-30 or even 0-30 is usually specified.
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On 11/07/2018 07:29, Brian Reay wrote:

Sludge can form in any grade of oil except Fully synth as its the product of oil mist and water vapour being overheated. When cooked Fully synth doesn't break down into the same sludge forming products that dino oil produces.
https://en.wikipedia.org/wiki/Oil_sludge
5w-30 and 0w-30 are unlikely to be dino or semi synth oil.
If your average speed is less than 15 mph you should be on more frequent oil change routine. Or make sure you do at least one trip a week that gets the engine hot enough long enough to boil the water out of the oil.
A coolant/oil heat exchanger can help as it not only cools the oil to prevent it cooking but also brings it up to temperature quicker.
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On 11/07/18 08:38, Peter Hill wrote:

Certainly more likely to be Fully Syn. these days. I'm not sure what 'dino' is, perhaps another name for mineral oil?
I've not used even Semi Syn. for years. I 'converted to it early on then to Fully Syn as I bought cars that needed it.
Rightly, or wrongly, I believe that regular oil (and filter) changes with quality oil go a long way to ensuring long engine life.
I do know someone who never changed his oil. He had at least one really old lorry type vehicle that he reckoned was on its original oil. He must have been very lucky ;-)

Interesting, thank you. However, you've rather exposed my basic approach / use of terms. I was using the term 'sludge' to the refer to general 'stuff' that seems to collect in the sump- at least of you change the oil at (say) 10k miles (or more, heaven forbid!). I tend not to see it as I change oil every 12 mths and don't cover anything like 10k miles in that time these days. In the days I did cover higher mileages, I changed at 10k (unless the car spec was lower). Also, I've not owned any vehicles on that list- although I assume other makes suffer.
Don't misunderstand me, I'm not suggesting you are incorrect- you knowledge in this area clearly exceeds my own, I was simply referring to something more basic.
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Brian Reay wrote:

Do you know of one with a pipe small enough to fit down the dipstick tube? I'm not sure how else you would reach it.
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On 11/07/18 10:16, Dan S. MacAbre wrote:

You can buy such pumps. I assume the pipes fit. I've not measured the inside dia of a dipstick tube but would guess at maybe 6mm or so.
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