EVER started an engine on a really chilly morning and noticed how much more sluggish it feels when cold, but smoothes out and gets more responsive after driving a few miles? That’s because engines work best and most efficiently when they are up to their proper operating temperature – on electronically-controlled engines, this is when the fuelling and emissions control systems are operating at their peak efficiency, giving the best performance and cleanest running conditions.
No matter the outside temperature, it’s the job of the thermostat to bring the engine up to running temp, and keep it there. When the engine is cold the thermostat should be closed, so that the coolant can only circulate around the engine itself and the heater matrix. This allows the engine to heat up more quickly, as there is a relatively small volume of coolant to contain the heat. When the engine gets up to temperature – normally halfway on the gauge – the thermostat opens and allows coolant to flow through the rest of the pipework and radiator, managing the heat and keeping the engine at the correct temperature for it to work at
