Question about possible coolant in oil

Joined
Jun 5, 2003
Messages
835
Location
McGregor TX
I changed the oil in my wife's 2012 Toyota Highlander (with the 3.5L) a couple of weeks ago. The oci was about 8000 miles. Toyota recommends 10K but I always try to change it around 7500-8000. It has around 150K miles on it. The oil coming oil looked fine like it always does. I took it to be recycled and thought no more about it. I pulled my oil drainpan out to change the oil in my son's car yesterday and was surprised to find a little evidence of what looks like coolant in the oil in what remained in the bottom of the drain pan. It was sort of reddish and a little gelled.

As I said, the oil coming out looked fine--no milkshake. And the coolant level was fine, although just *slightly* below the FULL line, which is probably about where it has been. So I'm trying to figure out if there really was coolant in the oil or if somehow something dripped into the pan while in my garage. I can't for the life of me think how this might happen. I don't use the oil drain pan for anything else.

Thoughts? We've put about 500 miles on the car since the oil change. Would that be enough time to drain a little oil to see if it will separate? *Will* it visibly separate? We're going on a road trip in less than 2 weeks, so I'm pretty pressed for time. I don't have time to get an oil analysis done before we leave. I'm thinking if there is a coolant (head gasket) leak it must be tiny at this point. I'm thinking I'll just keep an eye on the dipstick for signs of a problem.

Thoughts? Advice? Thanks in advance!
 
Last edited:

mrdctaylor

Thread starter
Joined
Jun 5, 2003
Messages
835
Location
McGregor TX
One additional thought as I wracked my brain: I did accidentally overfill the washer fluid reservoir and it overflowed and dripped down while I was draining the oil. I always do other things like that while waiting for the oil to drain. I’m wondering if some possibly got into the drain pan. The stuff I’m using now (forget the brand) is pink, which is the more or less the color of Toyota coolant. That might explain how the oil looked ok but the remnants looked contaminated a couple of weeks later.
 
Last edited:

JHZR2

Staff member
Joined
Dec 14, 2002
Messages
48,376
Location
New Jersey
Do a UOA. No other way to know….

Oil can hold a lot of antifreeze before becoming a milkshake.

Since oil is usually at a higher pressure, I’d anticipate seeing signs of oil in coolant if there was such an issue.
 
Joined
Dec 6, 2019
Messages
559
Location
South
If there is coolant in the oil there is always a grayish slim that collects on the PCV valve and/or oil fill cap. If there is none there no need for worry.
 

mrdctaylor

Thread starter
Joined
Jun 5, 2003
Messages
835
Location
McGregor TX
I made a note of exactly where the coolant line is on the overflow tank when cold. Took a pic. I’ll wait a week and see if there’s a change. There is absolutely no evidence of coolant in the oil on the dipstick or under the fill cap or in what I can see in the crankcase. The oil looks clean and as it should look on the dipstick. I’m beginning to suspect moisture got in my drain pan some other way. We shall see. Fingers crossed.
 
Top