JCL,

Thanks for your informative response. One of the reasons that I am concerned about the 4.4 engine in my environment is that I will be doing a likely mix of 3-5 short trips (2-5 miles in length) for every 60 mile trip that I take. Because of the heavy expense that can occur if the crankcase ventilation system freezes up, I will definitely be taking the beast apart and cleaning it up and replacing hoses/parts as soon as I purchase the new-to-me vehicle. I guess it might be advisable to do this inspection/cleaning twice a season in the winter.

My V8 Jeep is not nearly as sophisticated as the BMW in a number of ways, but at least I don't have to worry a bit about its crankcase ventilation packing up and taking the engine with it... I think I am still going to get the X5, though.

I've done quite a bit of research on this site concerning failure modes and the consequences of a frozen oil/water separator. It does seem to be a pretty serious problem that BMW could have done a better job in solving. Where was their long term cold weather testing program prior to entering production? Are there any home-engineered solutions that will keep these ventilation lines freeze-free in short mileage driving scenarios?