So I’ve bought a car (Buick Riviera 1980 3.8L Turbo), which had a blown head gasket and hasn’t been ran for over 12 years.

I’ve aligned the head to fit the block evenly, replaced the gaskets, did the oil/filter change, filled up the radiators. Started it up, cylinders work nicely, good compression, good oil pressure, although I’ve noticed a massive oil leak ( turbocharger return line was bad).
I check the leaked oil and color has changed to grayish. Car has been idling for about 5 minutes, oil pressure was still good.

Immediatelly I thought that water is being mixed with oil (which could indicate a bad head gasket again or cracks in a block), but could it be that it’s because of the fact it hasn’t been started for over 12 years and it’s just mixed with old oil (which was already gray due to blown head gasket in the past)?

I guess it’s just me coping, but I’d like to get second opinions on what could be wrong (or not).

Thanks a lot!