Steam indicates water ?, it also indicates a perfectly normal engine at this time of year, you have to take into account the DEW POINT, every 100 litres of air contains 940 grammes of water, if say 10C is assumed, this super heated water condenses when hitting a colder gas(air).
The easiest way to see is how the smoke behaves, oil mist will linger a lot longer in the air than normal exhaust gas containing moisture.
The higher the temp the MORE water content, seems odd but true, but also with higher temps less difference in extremes of heat out the exhaust to air temp, and it's enough to make it invisible.
I'm not saying it's not oil just saying to remember they can chuck out some serious smoke/steam at this time of year when temps are low.
Look into your down pipe, if oil is present this would account for it, when the turbine(exhaust) side of the turbo leaks it produces white smoke, as it doesn't get very hot, in comparison to being fried alive in the combustion chamber, this is what they do on films like with del boys reliant, pipe oil into the exhaust.
tabetha