Question

It is easier to start a car engine on a warm day than on a chilly day. Why?​

Answer 1

Answer:

With increase in temperature (i.e., on a warm day) the internal resistance of a car battery decreases. ... Due to it, the battery can supply large current which helps in starting the car enegine easily.

Answer 2

$\huge\fcolorbox {magenta} {blue} {Hey mate here is the answer}$

All that we need to start a combustion process is fuel,oxidizer and a heat source.

Heat source(In case of SI Engines it is a spark plug) gives a certain amount of energy(Increases the temperature of the reactants to its self ignition temperature) to start the combustion process.

If the temperature of the reactants(air+ fuel) goes down then more energy is required to increase the temperature of the reactants to its self ignition temperature for which the spark plug is actually not designed for.

During warm conditions you can start the engine easily but it reduces the volumetric efficiency of the engine due to low air density and hence the combustion efficiency of the engine goes down.