arthurY,
it's just a car, not a rocket or Ariane V. your question feels stupid in this context. your response anyway:
my so firm response as you say, is based on general observation. that's all I can say. it is sufficient don't you think? it the response of user lambda for a car model beta. take it on this basis, as to say, with no value.
now if you want figures make your own analysis, I have more interesting to do in life.
are you a scientist by the way? so typical of them to ask questions of this kind, but for interesting matters, I concede.