It's a freezing winters evening and I am stuck borrowing a tatty old VW T4 van after having some issues with my own car.
Wrapped up and wearing leather boots, I decide to warm the car up first by giving the big industrial engine some revs - to get the heating coming out.
It takes a little longer and the air blowing out seems to not change temperature, no matter how hard, how long or how much I red line that engine!!