Oiliy froth under engine oil fill cap?

[70marlin]

Just a noob :>) I'm looking to buy a used 325i 2.5L 02 or better so I've been doing a lot of test drives. I've noticed on all of the cars that I've driven a creamy light tan'ish froth under the oil fill cap, I pulled the dip stick oil levels looked fine no froth, is this normal. Normally this is a very bad thing? I'm a mechanic by trade just not on auto's for many years. I do all my own repairs.
Thanks Marlin
Sent from my SPH-D700 using AutoGuide.com App

[Lord Vader]

It can be a sign of condensation in the engine. It usually, key word usually gets removed when you drive the car for longer periods. On short trips their isn't enough hear to get rid of it. Which is why highway miles are always better for a car then short trips.

[Jack Dabsy]

I have to agree with Vader again... It should burn away after a decent run.
How's the coolant?

[70marlin]

Thanks fella's that works for me as these car look to be city commuters, my self I do a highway commute of 30 mile one way to work.

[Lord Vader]

I used to drive 40 km per way to work (80 km total per day) so I never saw that. It always got warm enough. The Milage adds up pretty good though!