"Creamy"? Well the ZDDP you will clearly see floating on top of the oil in a "grey/silver slick" when you drain the oil in the pan.
What I suspect what you are describing as "creamy" though is moisture in the oil.
That is what is supposed to be "boiled out" of the oil during opperation and fed back into the intake system and wind up dripping from your exhaust tips.
You have to have a properly functioning PCV and system. You have to get the engine oil hot enough to boil the moisture out. That STARTS, only starts as the oil temp approaches 185F. It really needs to get hotter then that though.
Boiling point of water remember is 212F.
I'd recommend that you use a 180 thermostat and when you run the car, run it for at least 20 minutes. If you don't you will just contribute to sludge build up and you won't allow the oil to wash the rust off the internal parts of the engine.
Oh, and use a detergent oil, not a racing oil with little or no detergency to it. It's necessary on virtually any street use vehicle and on cars like mine that see little mileage, mandatory.