Every single day the wind is the same direction and speed?And i doubt wind makes that much of a difference because cars are tested for aerodynamics to prevent drag in wind.
The most common causes of poor MPG are:
Under inflated tyres
Cold weather
Heavy right foot
Poor use of gears
Hills
Mechanical fault
Poor fuel.
Hills and cold weather can't be helped, the rest is down to the driver.
No, but on any given day if there's a south westerly on my drive in in the morning, then it's there on my way home, hence the tailwind/headwind routine.
Regards a cars drag, read this extract from Wiki:
"The drag coefficient is a common metric in automotive design, where designers strive to achieve a low coefficient. Minimizing drag is done to improve fuel efficiency at highway speeds, where aerodynamic effects represent a substantial fraction of the energy needed to keep the car moving. Indeed, aerodynamic drag increases with the square of speed. Aerodynamics are also of increasing concern to truck designers, where a lower drag coefficient translates directly into lower fuel costs.
About 60% of the power required to cruise at highway speeds is taken up overcoming air drag, and this increases very quickly at high speed. Therefore, a vehicle with substantially better aerodynamics will be much more fuel efficient. Additionally, because drag does increase with the square of speed, a somewhat lower speed can significantly improve fuel economy. This was the major reason for the United States adopting a nationwide 55 mile per hour speed limit during the early 1973 oil crisis as slower traffic would save scarce petroleum.
It's logical that driving with the wind behind you will be much more efficient than driving into the wind.