Does car colour have an effect on petrol usage?

Question

i asked this question and got a no. Here´s my theory: if a car is black then it absorbs more heat, therefore the metal on which it is painted will get hotter also. As it gets hotter it will expand (like railway lines requiring a gap between different tracks) and therefore will get heavier (or more dense?), thereby needing more fuel to give it thrust. A white car doesn´t absorb as much heat, so the effect is much less. If this is correct, then admittedly it will only be a small difference in petrol usage...but is it correct or am I just speculating?

Answer 1

As a metal expands it gets less dense but the total weight does not change. It might be argued that a an expanded car will have increased air resistance, which can be exponential, using slightly more fuel. I think that the psychological factor might be far more important. Perhaps people drive red cars faster than black cars, wasting fuel. More likely, people who like to drive fast will select red cars. Of course, it they select a small sporty red car they may actually save fuel. The problem does not compute.

Answer 2

That is your theory. Do some experimentation with the same make/model/age car in different colors and then you tell us.