Sorry about the repeat but I wasnt able to edit my post---Have same trouble as last post wanted to add that the smoke is billowing from the exhaust not the engine compartment.I am also running a a synthetic oil (could the smell of burning plastic/rubber) be the synthetic oil burning? Also is it possable it could be a head gasket blown thats causing a vacuum in the crankcase? Ive never ran across this type of problem before on any car. Again any help would be appreciated. There was no warning prior to the problem. The engine wasnt overheated,plenty of oil in the crankcase. Dipstick shows only oil,no froth or contaminates.After replacing o2 sensors I took for test drive. The smoke cleared after about a mile,seemed to be running ok.Upon parking It started to blow smoke again. Anyone have a clue on this? Thanks again.