if drain plug is low spot in pan, can you drain water out?

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Sep 12, 2003
Agree. Water would have to have been recently introduced, such as a significant head gasket leak, to retain separation from the oil and allow you to drain it out. In short order, the engine -- with all the thermal, chemical, and mechanical processes it inadverdently imposes on anything running through the oil channels -- will either put the water into permanent suspension or even possibly chemically combine the two (a chemist could answer that).
My Subaru is sporting a drain valve instead of an oil plug
And a thought occurred to me...

If water is denser than oil, if you accumulate water in your oil due to insufficient engine warm-up, would it make sense to drain a few ounces after letting the oil remain motionless overnight to get out that water?

This would only make sense if your drain plug location is the lowest spot in the oil pan (which it is for my car). How much water could be in there, too? A few ounces? Half a pint?
In theory this would work, but in practice the water and oil somehow seem to mix together.

My advice, that I practice on my wife's car, is to change the oil far more frequently due to the fact it never gets warm, ( water does, but not the oil ).

Also I still use a synthetic oil, although with info learned from this forum, a good dino oil would serve her needs perfectly.
An oz or two. The water accumulated in your engine, only comes from air within it cooling down after operation. Most of it would be clinging to the cooler metal parts and would probably be evaporated before draining back into the oil.

Here in the UOA thread you often see 0.5 to 1% of water in the oil. At 1% this equates to about 1.6 oz of water in a 5 qrt sump. This is probably coming form an engine that was warmed up slightly to drain the oil. The water was most likey mixed throughly, but not vaporized. So I think its a pretty accurate representation of H2O in your engine.

Is it enough to drain? Probably not. A 20min highway ride would vaporize that water, and it certainly would be more enjoyable than crawling under your car.
I have known of people doing this on large equipment with big capacity oil pans but on a little car I would think just changing at a shorter interval would better serve you.

As far as the amounts you listed I would not think you could even get close to that much water in there.

Also consider a high quality mineral base oil such as offered by Shaeffers Mfg.out of MO. or Cen-Pe-Co Lubricants out of Ohio. The synthetics offer many benifits but do not perform as well in rust inhibition tests I have seen. And if you shorten your drain intervals you will not be using the strenghts of a synthetic anyways.

I believe their web sites are Cen-Pe-Co.com and Shaefferoil.com Schaeffers makes great products and if you ever see tractor pulling on espn2 or nesn the Pullers love their Cen-Pe-Co oil. and those guys know how to challenge a base oil
Oh -
Nosmo brings up a good point too. Additives in the oil emulsify the water and keeps it in suspension. This allows it to vaporize easier when the engine warms up and doesn't leave a pool of water for the oil pump to pick up. 2 oz of water injected to the bearings would probably do some damage!
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