> The flat side faces the road

It would probably work a little better if there was some durable insulation on the "road" side, enduring more of the heat transferred to the pan.

But, as JCL says, nothing works as well as a real block heater, with the heating element directly in internal contact with the coolant, mounted in a freeze plug opening.

I would note that in very cold climates, such as below 0 degrees F, a block heater is used not only to ensure the engine starts, but to reduce the wear and tear on the engine during an extremely cold start and warm-up. i.e., just because it starts does not mean the use of a block heater is not a good idea.

> I don't see how it can impact the crankcase ventilation valve issues.


I am not an expert on the BMW PCV cold issues, but I would think that it might help in that a block heater would improve the odds the engine gets fully to operating temperature, and for a longer time, during cold weather drives, and, as a result, be more likely to purge moisture and condensation from the crankcase.

But I did say "might," as I do not know the details of the PCV issues.

I think the moisture that accumulates in the crankcase ventilation valve does so over a relatively long time period and not just when it is very cold out. The block heater is typically used only on very cold days. Yes, it is on those cold days that the condensate freezes in the crankcase ventilation valve and causes the common failures (oil leaks, etc) but the block heater doesn't heat that part and thus won't reduce the likelihood of it failing on those very cold days.

I just worry that people who are concerned about the oil separator will think that a block heater will reduce the chance of failure. The block heater is designed to help with very cold starts, ensuring that the wear from cold oil is reduced. Below -40, block heaters are a very good idea. From -30C down, they are a benefit as well IMO. At -20C I never bothered to plug mine in.

Of more benefit would be an interior car warmer on a timer. The use of that device allows people to avoid prolonged idling for warm-up, and that is definitely better for the engine. The interior is a comfortable temperature, the windows are clear, and the engine can warm up much more quickly by being driven moderately immediately after starting.