Time Vs Money: How Fast Should You Drive?

When the price of fuel soars, drivers who seek to avoid spending money on petroleum have two options. They can:

• Drive less, or

• Slow down.

For many, driving less is an obvious solution, but one that isn't necessarily achievable. That's comes down to why people have cars in the first place. They need them to travel to and from work and also to and from where they buy the goods and services they need.

In today's world, whether they drive a gas-powered, battery-powered or hybrid vehicle, some non-zero percentage of the fuel or energy needed to enable their ride will be produced by fossil fuels. When the price of oil and other fossil fuels rise, the cost of essential commuting goes up as well. But you can limit your exposure to those higher costs by slowing down to drive your vehicle at speeds where it is more efficient.

That fact was established by a nearly three-decade old study by the U.S. Department of Energy that found that most gasoline-powered vehicles in the U.S. are operated at speeds at which they do achieve their peak level of fuel efficiency. At highway speeds, for instance, the forces of aerodynamic drag can substantially increase the amount of fuel an automobile engine has to burn in order to sustain a high velocity. A simple back-of-the-envelope calculation reveals that the amount of drag force that a car being driven at 75 miles per hour sees is some 33% higher than the same car being driven at 65 miles per hour would see.

Though today's roads have more electric and hybrid vehicles driving upon them, they are still affected by the same laws of aerodynamics. Like gas-powered vehicles, it takes less energy to sustain them moving at lower speeds, which means their batteries can hold their charges for longer.

But not too slow. Driving too slow also comes not just with a time penalty but also an increased penalty for fuel consumption. Most modern vehicles are designed to operate most efficiently at speeds ranging from 30 to 55 miles per hour. That's the sweet spot in which you can get the most distance driving out for your fuel consumption dollar.