It surprised me.

Now, this isn't exact, as it idled for five minutes, since I started the engine when we arrived at the vehicle with the luggage cart to load it, but the coolant reach steady state after about 20 minutes (including the initial five minute idle). Of course, it was not a straight line, and most of the temperature increase took place early at a higher rate of change, so I'll give a few data points to give you an idea of the warm-up curve.

Initial conditions (according to X5 OBD-II data)

10.4 degrees F ambient, 12.2 degrees F coolant.

02 minutes 10 and 43

03 minutes 10 and 54

05 minutes 12 and 68

Then started the drive to the interstate...

08 minutes 14 and 113

Entered the Interstate at about 9 minutes and drove at 50 MPH initially...

09 minutes 16 and 123

10 minutes 10 and 147

12 minutes 08 and 160

15 minutes 08 and 167

20 minutes 08 and 176

23 minutes 08 and 183

29 minutes 08 and 185

Then it stabilized at 185 and stayed there for the next hour while I cruised at about 70 mph until I stopped at a rest area.

I forgot about the initial idling on that stop while I loaded the vehicle, so I'll check the data and see if I can find one more representative of a normal start without the long idle at the start, and post it. Maybe I can even figure out how to export the graph with the curve, as it give a clearer picture.

So, roughly speaking, I'd say it would normally take 10-15 minutes from a cold start at 10 degrees to get to 90-95% of operating temperature.

My plan to to collect enough data that I get a good idea of how long it takes to warm-up at various temperatures so I can make an estimate, since we have no temperature gauge any more, e.g., from zero, 32, and 70.