No Trouble code appearing, White smoke from tail pipe, Help!

By your discription we know the oil was very 'viscous' (yogurt like consistency) but what color was the oil or what flavor yogurt? .. Was the oil level overfull? .. Did the temperature gauge indicate the engine was getting hotter than normal? .. Was the coolant level still FULL? .. 'White' smoke from exhaust is indicative of 'excessive' (raw) fuel or coolant burning through the combustion chambers .. I feel sure the repair facility mechanics have already performed the usual test, i.e. .. Full scan test .. Combustion leak test .. Cylinder leak down test .. Cooling system pressure test .. Very difficult for anyone to diagnose without vehicle present for actual hands-on testing! .. Maybe have another repair shop check it out... Good luck! http://repairpal.com/repair-shops