Vw beetle tdi

[Mk2_tel]

 I own 2 and both seen to have slight white foam once I open oil cap.
I have been told its condensation this correct?

[scarr89]

Not too sure.

I think a whiteish residue on the cap is a sign of head gasket failure?

[LittleReDuck]

Is there white on the dipstick?
What is coolant consumption like?

If its eating coolant and the dip has white foam then it points to head gasket.

Wipe off the crud and check again after a drive, if its less and the car has been stood then its more than likely condensation.