5% at 70 mph is 3.5 mph 10% at 30 mph is 3 mph I saw this with various European cars. My experience is that it seems to be a fixed percentage rather than a f

5% at 70 mph is 3.5 mph 10% at 30 mph is 3 mph I saw this with various European cars. My experience is that it seems to be a fixed percentage rather than a fixed amount i.e. the absolute difference increases with speed.