Does a car cabin warm up faster by turning on the heater fan right away, or by waiting for the engine to warm?

Question

After a cold start in sub-zero weather, my friend and I argued about the fastest way to warm up the inside of my car. I would always start the car, drive for few minutes, then turn on the heater fan once the engine temp had more or less peaked. My friend, however, claimed that the fastest way to warm up the cabin would be to turn the fan on immediately after starting the car (and at full blast, ideally), thus blowing in cold air before gradually warming up.

I say my way is faster since you are allowing the radiator coolant and heater core to accumulate heat before displacing it into the air with the fan. My friend says his way is faster since you get the first traces of engine heat right away by turning the fan on immediately after startup.

Is my method faster, or is his, or does it theoretically make no difference between the two. Pros? Cons? Is there anyone who has expertise in the transfer of heat who could settle this for us once and for all? Thank you all.

Answer 1

You are correct. The heat is generated through the engine block. Furthermore, the heat will warm up fast by driving the vehicle than letting it idle as you are turning more revolutions while driving the vehicle. Besides, who likes to feel colder from blowing cold air around the cabin. Old timers probably insist it is better to let your car warm up first before driving it but the cars of their time were wore out at 50,000 miles.

Answer 2

Car Cabin Heater

Answer 3

Any one with knowledge of engines and your car owners manual, if you bother to read it, will tell you not to idle a cold engine to warm it before driving. Start off slowly and drive slowly for a few minutes to let the engine warm gradually. Turning the heater on high isn't the fastest way to warm the car. As the temp gauge starts to move off the cold mark turn the heater on low. The slow fan speed will move just enough air to start heating the car without overpowering the barely warm water moving through the heater. Once the gauge gets up to normal then turn the fan speed up.

Answer 4

Blowing the air immediately will cause the temperature to rise faster.

However, it also means you have cold blowing air (aka draft). Your perception of the temperature will be that it is colder even though the average temperature will be getting warmer.

Think of it like standing in front of a fan. The fan doesn't change the temperature - it just moves air around.

However moisture evaporating off your skin into the wind definitely makes you cooler.

Answer 5

if your in sub 0 weather i assume you're letting the car warm up for a couple of minutes anyway. start the car, turn heater control knob to hot/defrost, go in finish your coffee, then come out and crank up the fan.

Answer 6

let engine warm up for 3-5 minutes then turn on heat.