Originally Posted by PWGuy
Wow, I'm surprised by this to say the least. Ok so let me ask a different way - is it better for the engine internals, etc to warm-up the engine while parked in my driveway 10 minutes before a super short trip, like my wife driving to work? (Putting MPG aside)..
Yes. With your short trips which are not long enough for everything to reach nominal operating temperature, a best practice would be to let it idle at least 10 minutes before driving especially in temps below 50*F. Granted, you are burning fuel that isn't moving the odometer so fuel economy will go down...but....you aren't really going to be impressed with your mileage if the car never gets warm enough for closed loop either.
Thermostat, hoses, moisture in the oil, the catalytic converter, oxygen sensors, fuel vaporization, transmission - all are systems that REQUIRE a certain temperature in order to operate properly. Systems designed to be heat cycled should be expected to fail early if not properly heat cycled. My professional opinion is that the extra $ spent on wasted gas as it idles (marginal amounts, really) will more than offset the cost and hassle that may result from inadequate heat cycling.