Has anyone else seen these signs on billboards and at petrol stations? Basically it states - Think! Driving at 70mph uses 10% more fuel than driving at 50mph! Now, what I'm wondering is - If I drive at 90mph, will that use just a further 5% fuel? But seriously, what is this supposed to be telling us; drive at 70 cos it's more fuel efficient? For an extra 40% speed it's only 10% fuel... Hmm... Can anyone explain?