It is easy to say that fuel usage increases with speed, and that wind drag is the major increasing factor.
But just how great is the effect?
Is it the same for all vehicles?
Does driving slower always save fuel?
Lets look at some hard data: page 29 in Chapter 4 of Transportation Energy Data Book: Edition 30 - 2011, published by the The Center for Transportation Analysis at the Oak Ridge National Laboratory gives some figures for a variety of vehicles sold in the USA. Most of the vehicles reach their best economy at either 50 or 55 mph, with some of the physically larger cars better at lower speeds than that, and just one (the Toyota Celica - a reasonably aerodynamic sports coupe) being most efficient at 60 mph.
If that link is unavailable, then try here, which is a summary of the various data from the same source.
Just pick out the data list you think is the most relevant for you needs.
They all point to pretty much the same conclusions, whichever you pick.
Some important conclusions can be drawn, whatever type of automobile you drive, and whichever data source you choose:
But just how great is the effect?
Is it the same for all vehicles?
Does driving slower always save fuel?
Lets look at some hard data: page 29 in Chapter 4 of Transportation Energy Data Book: Edition 30 - 2011, published by the The Center for Transportation Analysis at the Oak Ridge National Laboratory gives some figures for a variety of vehicles sold in the USA. Most of the vehicles reach their best economy at either 50 or 55 mph, with some of the physically larger cars better at lower speeds than that, and just one (the Toyota Celica - a reasonably aerodynamic sports coupe) being most efficient at 60 mph.
If that link is unavailable, then try here, which is a summary of the various data from the same source.
Just pick out the data list you think is the most relevant for you needs.
They all point to pretty much the same conclusions, whichever you pick.
Some important conclusions can be drawn, whatever type of automobile you drive, and whichever data source you choose:
