My car got this problem as well and I'm sure the oil on the 2nd spark plug head and tip is engine oil, as I need to top up engine oil every 1000km. There's no engine oil discovered on other spark plugs. There's no white smoke coming out from the exhaust but the exhaust fume smells like white smoke. Previously before I send my car for engine gasket change, I encountered no such problems. Could it be valve seals worn out? I remember during the gasket change, my mechanic did change the valve seals as well.