zriha said:No, it doesn't, I talked with several mechanics about it, and they all agree, it is good for an engine (if not fully conservated) to start it up once in a while.
Just to be clear, you don't rev it, you just start it and leave it to idle for around 20-30 minutes (I often sit in the car and make some calls or something to pass the time). Why it is good - the temperature will go up in the intake, exhaust and the engine, at temperatures in 0C and minuses, it is good as car like that, outisde is protected by that heat for several days.
Option B is if you don't want to use it, then the battery is out, the oil is drained in the spring when you want to use the car.
For instance, in upcoming several days here in Croatia, the temperature will go well above 10C during the day, and it will be dry, no rain, so I will drive my Z4 as much as I can. Next week when it will go rain and lower temperatures, it will sit under the cover with occasional 1-2 start up-s.
Also, BMW's has a problem with exhausts that are only sitting outside, with water condensation, so it is recommended to warm the pipes up.
If I had a garage, it would be the whole another story, but I don't.![]()
I am not sure it does any harm in particular to the engine, but the BMW manual does say specifically not to do that. It may be to cover their asses in case the engine cannot get enough air while stationary, but I can't imagine for a second it would struggle to get enough air at idle revs. Here is the section from the manual btw:



