New f150 owner here. 2000 f150 4.6. I've read it's really common for condensation build up in filler neck. Almost s**t my pants when I discovered it today. Anyways, I checked my dipstick oil looks good and coolant level is good. So I'm assuming it's condensation. I do live and work in town so short drive cycles plus it's been below freezing all week. With some delightful -10 night temperatures. I also just replaced pcv two weeks ago and inspected evap system. Everything looks good. My concern is after cleaning the milk I drove it for 40 miles got home and let it sit. Checked the cap and same thing? Not as much but definitely there. Change the oil? Faulty pcv?( did buy at advanced, not a motorcraft part) Should I just go to sleep?

 

I get the stuff myself. I don't worry about it as it is harmless where it is at. All you can do make sure PCV and breather line/ filter are clear, make sure your engine is running up to proper temperature or drive it more to burn it off. I wouldn't go changing oil unless you reached your mileage interval. Good night!

 

To add to that, you most likley had quite a bit under the covers. It builds across and sticks to the top of the cam covers. 40 miles didn't clean it up or burn it off totally. Had the same problem and just ran down the e-way every now and again for about 10 miles. Just in the winter to burn off residual moisture in both engine and exhaust. Yea the exhaust loads up as well this time of year, just water.

 

And to just add, You should get a Motorcraft pcv valve.

 

So long as the oil on the dipstick look good, you should be fine. The high filler traps the moisture that is trying to burn off so will be the first thing to get the milky buildup, but as said, you can have some buildup in other "high" parts of the engine as well (valve covers).
Not sure what your current oil change interval is, but you may want to shorten it a little bit.

This is my oil filler cap last February with 5000 miles/10 months on the oil.

I could see some milky oil in the fill tube as well, but dipstick looked fine. I am a mostly short tripper (3 miles each way to work) with an occasional 50 mile each way drive monthly. This was what it looked like the day after the 100 mile drive. Temps were not even at the freezing point for months, but lots of humidity.
I changed it that day, but was planning on changing it even before I saw the buildup.

 

So I cleaned the neck and cap off this morning, and did a pressure test on cooling system. Came back good. Then went and ran the truck for an hour.


oil looks clean on dipstick, a little build up on filler neck and cap but nothing to crap my pants over. I think we're good. Thanks for the replies and information.

 

yeah I ordered one from Amazon today 9$