If you can find no mechanical explination. Try this product. You can find it at any truck stop.

I wouldnt quite on the car yet.

In Minnesota and Wisconsin winters, what you see is in many engines all winter long. The real problems arrise when upper engine components dont get sufficient lubrication due to contaminated oil. BAD

Rislone obsorbs and disipates moisture vapor and sludge in deisel fuel and engine oil, also improves lubrication. If used in a clean engine known to be susceptable, it will stop sludge from forming.

This is a common problem with large sump engines that dont get driven to full operating temp. regularly or in your case a engine that isnt working very hard very long.

With no coolant consumption it doesnt sound like a gasket leak.

It is true as stated in previouse post ring blow by or poor crank vacum can cause this. It is like a air compressor drawing undried air, high (Head)and low (sump)temps under pressure create condensation. DEW point generators work on this principal. The additive will help disipate the moisture as it forms.

The oil consumption could be caused by the dilution of the oil.

Just my .02