Your milkshake may be because of condensation in the oil. It is hard to heat up the oil in these engines in the winter, they seldom get above 180 degrees unless you drive it hard.
I suggest you change the oil and look around for a mechanic that can check the oil for antifreeze. At 3,000 rpm, the oil pressure should be greater than the coolant pressure, making a real mess of the fluid.
If your mileage is less than 20 in stop and go traffic, check for vacuum line leaks. Especially the elbows at the intake manifold and under the battery tray.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)