It is better to drain oil rather than use an oil extractor because it seems the extractor will leave behind some a significant amount of oil whereas a drain will get out significantly more.

However I take it’s still ok to use an extractor since the remaining bad oil will get mixed with the new oil. But since the overall quality is lower it simply means your engine or transmission never gets really fresh oil but you just need to do oil changes more often e.g 2-3 times a year rather than evey year?

Would you agree?

Or would The difference In a yearly drain vs regular attraction affect the engine significantly can’t such that it’s better to do a drain everytime?


  • If depends on the engine. Change the oil several times a year when the manufacturer specification is every 18,000 miles / 30,0000 km would be ridiculous. (And my own car, now 12 years old, still only needs one top-up of half a liter mid way through the 18,000 miles).
    – alephzero
    Commented Oct 11, 2020 at 20:05

2 Answers 2


If you drain the oil, hot or cold, and wait 2 days for all the oil to drain out you still won’t get all of it out. Just take the engine apart and all the surfaces will still have a thin layer of oil on them.

So most of us just get the largest part out and then the ratio of new to old is high.

If you really want to make an effort then drain the old oil, fill with a cheap temporary oil and run the engine for a few minutes, then drain that and fill with the quality oil. Why don’t most of us do that? Because we know it’s not worth the time, or cost, for such a small difference.

  • It also creates a lot more waste to run temporary oil. Getting rid of what you drain out is sometimes a pain to recycle or what have you. Now, double that. Great fun. Commented Oct 11, 2020 at 19:31
  • @Pᴀᴜʟsᴛᴇʀ2 so just another way of saying my last point.
    – Solar Mike
    Commented Oct 11, 2020 at 19:54
  • In what part of your answer do you mention waste? It creates more waste. I agree with what you wrote ... just think you neglected a point was all. Commented Oct 11, 2020 at 23:10

Extracting the oil is perfectly acceptable. Certain cars ("Smart" if I recall correctly) don't even have an drain plug anymore. The residual amount of oil, assuming no mistakes during extraction, isn't relevant.

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