Mayonnaise=water-oil !!!!
 

Well I am new to these forums and alas I have a hard problem with my pickup.
I have a 99 f150 5.4l it has 78,000 miles I bought it used. My problem is I went to get my oil changed and the guy took the oil cap off it looked like mayonnaise he said it was from oil and water mixing and not letting my truck warm up. But I let my truck warm up every morning before work and after work for at least 15 minutes could I have a seal broken, I live in oregon at the beach and it rains alot? Anyone have any Ideas and no I have not driven through an large mud puddles or rivers or lakes or even the ocean frustrated beyon belief LOL...

If it's just on the cap, don't worry it's just condesation and is a normal byproduct of the combustion process. It's more common in the winter because the valve covers do not get hot enough to evaporate the water out of the oil on the insides of the valve covers. It's pefectly fine and normal.

Now if the oil on the dipstick looks white or milky, you have a major issue. This would most likely be a head gasket, but it could be a cracked head or block.

great that is awesome to hear because it is not on the dipstick it is only on the cap great thanks whew LOL :D

IMO letting the engine warm up does nothing to help the engine, but it is nice to get into a warm truck:) I let my truck warm up 10-30 seconds and drive off slowly 'till it warms up.

My trip to work (train station) is only 2 miles each way. I get plenty of white gunk under the oil cap this time of year. Never happens in the summer.

i also drive a short distance to work thanks for the help gentleman puts me at rest lol

short trips will make it do that.my job is only 5 miles from home. i take her on the highway on the weekends drive 10 -20 miles let her breathe.

short trips and long idle times are the worst thing you can do to these trucks.

I would let it warm up less and take the senic route to work. I would also change the PCV and change the oil more frequently.

What is happening is when you first start the engine it produces a ton of water and because you let it sit there and idle the water just goes past the rings and into the oil. then you drive a short distance and never really heat the oil up enough to "boil" the water out. I'm not talking water like a head gasket leak.

And if the guy that changed your oil didn't know about this run as far away from him as possible and find someone that know what is going on.