No one enjoys stepping into a cold vehicle that’s been sitting outside covered in frost with the windows all fogged up. What’s the solution? Starting the car and let it idle away for 30 minutes until the cooling system can take over and supply the much needed warmth? Sounds great, but it may not being doing the vehicle, your pocket or the environment any good.
Back in the day when carburetor-equipped vehicles were normal, cars were practically undriveable until the engine was warm enough for the choke to be disengaged. We’re sure anyone who was ever running late for work has tried this and ended up bunny-hopping down the road, severely under-powered and with black smoke puffing out the exhaust. It’s a bit like being woken up in the middle of the night and being expected to run a 100m sprint. Momentum is hard to achieve and all you want to do is lie down and sleep. This was alleviated slightly by the invention of the auto choke, which would activate on start-up and slowly reduce as the engine warmed, and was evidenced by a high revving engine while parked at the lights or intersections.
Fast forward a few years and it’s safe to say that most mainstream cars on the road would be equipped with a fuel injection system. This modern system is computer controlled and adjusts fuel delivery based on temperature, throttle setting and engine load. This enables your car to be driven almost immediately, even at low temperatures.
The science and engineering behind engine performance is relatively straightforward. Metal parts expand and contract and they’re designed to work best within a specific temperature range. The efficiency of fuel combustion also varies with temperature. Simply put, a cold engine burns extra fuel. The catalytic converter or DPF (diesel particulate filter) installed in a vehicle’s exhaust system is less efficient when it’s cold. This is another reason why short warm-up times reduce emissions.
The goal is to get the engine into its preferred temperature range quickly. The best way of warming it up is to drive the car as soon as possible – about 30 seconds after you’ve started the engine – and taking it easy until it reaches its ideal operating temperature, which is when the engine is also at its most efficient. Running an engine when it’s cold causes increased emissions and engine wear, so driving loads the engine and warms it more than extended idling.
If you need to de-mist your windscreen start the car, give the windows a squeegee and wipe with a cloth. Turning on the rear demister, mirror heaters (if you have them) and A/C acts like a dehumidifier, clearing your vision and by that time the car should be warm enough to drive, with the heater kicking in soon after.
Comfort aside, gone are the days where a vehicle actually benefits from a lengthy warm-up and if there are continued problems experienced when a vehicle is cold, it might be best to get the car checked by a professional.