When started from cold (0 degrees celcius or less) my car blows blue smoke until warm. Why?

Could be one or the other or both. If you have a blown head gasket it could allow water to get into the cylinders and this would also cause blue smoke. Check your oil, smell it, feel it. Does it smell burnt? Does it have any water in it (oil and water don't mix so it would be separated). How about the color? I would get some Lucas Oil and run it as long as you can. If the car is not burning oil to the point that you can't keep it full, and if you don't drive your car like a race car driver or full throttle then hard brake, you could conceivably get another 40,000 miles out of it before you have to replace the rights or valve guides and/or seals. The cost to have these done is about the same as to replace an engine.

Lucas Oil will help. Also, you didn't mention how many miles you have on your car. If it is high mileage, I would use Castrol high mileage oil. It does help. I use Lucas for power steering, transmission, and for oil. It's excellent!

check the air cleaner first(no matter what a new one will help). The spark plugs may need changing too(to hotter ones) . The choke valve is on for that duration so restricting the amount of air getting into the engine and the engine will take air from anywhere it can get it, so most likely the valve seals would be a first check.

You would not need to plug it in overnight....plug it into a timer for maybe 1-2 hours before you would normally get out to start the car in the morning. That should be enough.

0 as 0/0 is 0

Ye probably valve seals oil leaks by into the combustion chamber overnight and then it'll burn up and eventually be gone..untill it sits for a while..

valve guides worn, needs cylinder head work to much work

just keep driving will not really hurt engine

i would say its valve seals. oil is leaking past them and getting on the valves, and when you start it, it burns the oil off.