How do I clean out engine oil that has water emulsified in it? My engine oil looks like Thai peanut sauce and smells a bit like gasoline. I'm 99% sure this is from combustion vapor getting into the crankcase (worn rings, valves not closing properly) and too many short trips in winter weather. I plan to address the root cause in the next few months by rebuilding the engine. In the mean time, what should I do about the oil? Obviously I'd like to replace the oil but I know the mayo won't drain out.

What I've already done hasn't helped. 2 days ago when I checked the dipstick it was below the fill line and looked like mud. The inside of the fill cap had the mayo in it. I wiped that out and added a quart of new oil. Then I drove 50 highway miles, hoping to get the oil hot enough to boil out the water. But that didn't do much except maybe move it around. Now I have mayo on the dipstick too.

Make sure your thermostat and PCV valve are working properly. Get some cheap oil and do a couple of oil changes.
This time of year 50 miles likely isn't enough time to boil off a lot of moisture. So, longer drives will help.

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I grew up in Anchorage, Alaska and condesation in the oil was a very common problem in winter. Best cure is to make sure you are running the correct temperature thermostat and occasionally take the car for a long highway drive to boil off the water. Otherwise, changing the oil is pointless since it will get contaminated again in short order.

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I have the 190 degree thermostat, and the coolant temp comes up to normal range within a few miles of driving. But my daily commute is only 5 miles each way (it's a good problem to have!), so by the time I get there the head is barely starting to get warm. I'll try some more highway driving and see if the oil clears up any.

Yep, drive 30-60 min and see what happens.

Lou

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You can also block off part of the radiator to reduce the air cooling of the engine.

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Joshua

Carefully clean out the engine with soup mix if you're sure the water in the oil is only water and not coolant from an internal leak. If coolant (ethylene glycol) has got in, you'll need to add butyl cellosolve to the soup recipe.

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Too many people who were born on third base actually believe they've hit a triple.

I've wanted to build a oil cleaning centrifuge and achieve the extended oil changes by cleaning the oil every 3,000 miles - adding a quart of fresh oil. After a 12,000 miles replace all of the oil with fresh oil. There are cheap centrifuges on Ebay, I'm sure these are cheap for a reason.

Engine oil centrifuge systems already exist. They operate continuously as the engine is operated. In most use cases they never pay for themselves. With modern engine architectures, controls and oils 10,000 mile oil change intervals are not a big deal. If you really want to use less oil then drive less or drive a more efficient vehicle. If you want to clean oil as a hobby that's another story.

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Joshua

I'd want the cleaner oil for use as heating fuel in a furnace. I don't think the small engine oil pressure driven centrifuges work very well for removing water - these can remove some soot from diesel motor oil. I can build a small centrifuge with my lathe, the self cleaning models that can operate 24 x 7 are more difficult to build, but I don't need that much filtering. Once water is removed from used oil the settling method can work okay if you've got time to wait and the weather is warm. You can remove the water with settling too. A lot of the cost of city water treatment can be the electricity for removing solids with huge centrifuges from the water that is pumped from rivers and lakes.

Change oil and filter while it is hot, and go for a 100 to 200 mile ride on the interstate. That should dry engine out, as well as the exhaust system which also is saturated rotting from within.

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