Originally Posted by IH84DZ
.......... 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........
Achieving normal operating temps (and closed loop mode) is indeed important for engine health. However bad gas mileage and engine wear issues will definitely NOT improve thru an idle warmup strategy. A car engine will consume almost as much fuel in 15 minutes idling as it takes to drive 2.9 mi cold....and it still needs to drive the distance. Gasoline engines consume lots of fuel at idle, especially when cold. Any car seeing trips under 5 miles each way is doomed to early demise. This car needs to see extended weekly drives for some other purpose to keep snot out of the crankcase.