Engines are mechanical systems designed to work optimally in a specific temperature window, so all elements suffer especially at start-up and during the first few minutes of use.
Cold and optimum operating temperature
To explain what happens inside the engine of a car when starting cold, we are going to retrieve a video published by the Engineering Explained channel. It shows the operation of an engine under the prism of a thermal camera that graphically displays the temperature of each element through a color code.
After a cold night, when starting the car’s engine, we must bear in mind that we can demand practically nothing from it, other than to keep it turning. A good idea before asking the car to start is to depress the clutch pedal to relieve the starter motor of the overexertion involved in moving the clutch and the gearbox oil (valvulin), an oil that is very viscous and tends to harden in the cold.
We must treat mechanics with kid gloves so as not to force premature wear. It is not necessary to let the engine warm up at idle. It is enough to let a few seconds pass to fasten the seat belt. What we must bear in mind is that when starting off we must be gentle when using the accelerator.
An unmistakable sign that the mechanics need some time to adapt until the necessary temperature is reached is the idling speed. When the engine is cold, the control unit keeps the rev range above 1,000 rpm and gradually lowers it once the engine begins to warm up.
The hot spots will begin to enter a temperature close to optimum, and will do so more rapidly near the combustion chambers, cylinder head and exhaust manifolds.
The temperature rise spreads out as the coolant manages to warm up and stabilize the engine temperature at around 95ºC. It is not until some time later that the control unit lowers the idle speed to below 1,000 rpm.
At the moment before starting, moreover, all the engine oil is at rest in the crankcase. The oil pump must be allowed to suck up the lubricant and distribute it throughout the engine. In addition to its own lubricating function, the oil has cleaning properties to remove particles that can damage internal parts, and it also cools the engine and distributes the temperature evenly.
At very low temperatures, all fluids become thicker, i.e. the oils used either to lubricate the engine or transmission, or the hydraulic steering or brake fluids, will hardly be at their optimum working temperature when the car is cold.
Therefore, for very low temperature zones, it is advisable to use a multigrade motor oil in the engine that maintains its fluidity in winter. And to know if we are in front of the correct oil we must know how to read the code that identifies it.
For example, a 10W-40 oil will be indicating us:
- 10 as the minimum SAE viscosity grade.
- W stands for ‘winter’.
- 40 is the SAE viscosity grade at operating temperature (hot).
Cold weather does not only affect the mechanical part of the vehicle. The drop in temperatures can cause engines to start worse due to a cause directly related to the electricity they need to start their operation: the loss of power of the batteries we use to start the engine when they are affected by the cold.