Petrol Consumption by Speed??

[martinw70]

Does petrol consumption change if you travel at different speeds? If so how much does so?

[Bob Carter]

Given that everything else is equal then the consumption falls as speed rises because the biggest factor is drag, that is, air resistance. Someone with a better memory than me will put in the equation but as speed increases by X resistance increases by X squared.

[Mattk]

i wouldve thought consumption is relevant to engine revs ie how hard the engine is working.cars are usually designed to run at optimum rate at 56mph

[dodgyshirt]

It is a misconception that cars are designed to give optimum fuel consumption at 56mph. Fuel consumption varies according to several factors, one of them being speed. In order to give comparative fuel consumption between different makes and models of cars they are all tested at speeds of 90kph and 120kph to name two. Of these 90kph converts to 56mph. The majority of cars will in fact return a better fuel consumption at speeds lower than this even.