Make it 0 and nobody will even need to run their engine at all.
Anyway, given the speedo offset on modern cars, people doing 60mph incidicated are probably doing around 56mph actual (well, nearer 58, but still close to the 'optimum' speed that is only that purely because of benchmarking).
Anyway, given the speedo offset on modern cars, people doing 60mph incidicated are probably doing around 56mph actual (well, nearer 58, but still close to the 'optimum' speed that is only that purely because of benchmarking).