White Residue on Oil Cap

[akuska]

I just checked the oil level on my car and opened the oil cap to look inside when I noticed a little white residue on the oil cap and on the rim where the cap screws in. It looks almost like cafe au lait. It's too dark, so I can't see into the crankcase when I remove the cap. However, the oil on the dipstick is still very dark.

Should I be concerned about this? I've looked on some other sites, and get answers ranging from "it's just a little condensation, don't worry about it, all cars do this in the cold" to "there may be coolant or fuel dilution and you may be damaging the head gasket" and everything in between.

Here's some background:
I'm running Castrol Syntec 5w40 on a 2006 VW Jetta with the 2.0T engine. It's been 7K since the last oil change. The schedule is 10K. The car has about 26,000 miles on it now.

We just had a stretch of 10 consecutive days where the temperature never got above 20, and for most of that time we were in the single digits or below zero. Today's the first day near 30 (it feels downright warm!), so it's the first opportunity I've had to take the time to check the oil. As I noted on another thread, I am in the minority who doesn't warm up a car for very long before driving off (slowly, under 2000rpms for the first few minutes). The car gets mostly highway miles at night (city and mild rush hour traffic in the morning) and I have a 20-30 mile commute each way most days.

I usually check the oil level every 1000 miles or so, but because of the cold and a few out-of-town trips, it's probably been about 1200-1500 miles since I last did a proper check.

The car has boiled off almost no oil over the past 7K miles. Previously, the dealer used Mobil1 0w40, which I topped up with GC or M1. It used to boil off about a quart every 5K or so with that blend.

 

[JAG]

My guess without a picture that it is H20-infused oil. My mother's '99 BMW 328i gets ugliness like that on the oil fill cap. And the other day, I managed to create this type of nasty soup artificially by mixing oil and vinegar and heating it to about 210F. It looked like a cappucino when I stirred it up.

 

[Chris142]

Taste it. REALLY! Then you will know if it's antifreeze or condensation.

 

[Big Jim]

It may be normal, but again it may be an indication of an ineffective PCV system (plugged valve) or even coolant crossover into the oil.

You should at least check the PCV valve and make sure it isn't plugged.

 

[Triple_Se7en]

You probably removed the cap on a day - or within recent days when alot of air moisture was present. Was the vehicle parked for a day or two during all-day rains or snow - then the oil got checked?

 

[Ramjet Roger]

Depends on the vehicle, driving conditions, how much residue, and lots of factors. I have Dodge Hemi v8. In the winter (mid-atlantic 10-30F temperatures), I find a bit of moisture underneath the oil filler cap every week. Most folks with the same engine report the same. Generally, short trips in the winter don't enable the moisture from the blow-by gases to evaporate from the inside of the engine. When the engine cools, the vapor condenses. As long as the amount of condensation is small and you UOA is acceptable, it's nothing to worry about.

 

[akuska]

Thanks for the info. We did get a little bit of snow last week (about 2-3 inches), and I vaguely recall the oil cap being slightly unscrewed (perhaps just 1/16 turn) one time when I was refilling the washer fluid. The coolant when I checked my car was about 40% between the Min and Max lines, although I had just driven for about 30 miles and the engine was hot. I don't remember where the coolant usually fills to in the reservoir. If I think of it, I'll check the coolant tomorrow morning before I start the car, and then check the oil cap later on tomorrow and later in the week to check the color of the oil that splashes up. It is going to be a little snowy, but warmer the next 2-3 days before it gets back into the lower teens and single digits.

 

[akuska]

BTW, as for the amount of residue, there appeared to be just a little bit under the cap and on the rubber gasket where the cap screws in. The oil on the dipstick was dark and flowed normally. I wiped off the cap and the rubber gasket, and noticed that the texture was a little "gunkier" than the oil.

 

[Syntec-Man]

One day my dipstick had white residue on it :O It was snowing that day i think. never thought of it much then but ???

 

[Dr. T]

We had the same cold spell up here in Toronto and I too was surprised to see how much white gunk I had under my 3L BMW engine oil cap too...even after a longer drive....and I use LC.

I really think the smaller-OHC engines take a long time to get the condensation out, especially when the temps are that cold and the manuf. put baffles in (so you can't see inside) that trap things further.

Nothing to worry about...especially with the 5-40 (A3)...nor is there a need to check the oil every 1k mi. either....in that cold with that quality oil. That's for those using cheap 5-30 or if your engine had 126k mi!