Showing posts from January, 2015

Car speed and efficiency

Call me somewhat obsessed if you like, but ever since acquiring a car (2006 Renault Scenic) with an actual computer inside, along with a miles-per-gallon readout, I've been taking rather an interest in the efficiency at various road speeds. Yes, I realise that petrol has become cheaper in the last month or so, but it was downright pricey for most of 2014, so every gallon saved is the best part of £10 back in my wallet.

So what IS the most efficient speed to drive along at? Classic car manuals and Internet advice often throw up '56mph', but then we've seen that speed quoted from as early as the 1950's, when car shape and aerodynamics were incredibly primitive. Surely modern cars, designed in wind tunnels, should be able to slice through the air better and this should have some effect on fuel efficiency?

[The problem with going fast is that there is far more air resistance - this increases as the square of velocity, so there's four times as much drag to overcome a…