I do not think so everyone really likes filling up the gas tank. It’s like you’re right there when you could be going somewhere. If you have gas on your hands or shoes, you can smell it all day. And on top of all that, you actually have to pay for it. With gas prices over $4 a gallon (up to $6 in some states), we’re all too painfully aware that gas doesn’t come cheap.
Of course, there are plenty of things you can do to spend less at the pump. The US Department of Energy has some tips to help you save fuel, including removing cargo on the roof and extra items in your trunk, using cruise control, and even turning off your engine while waiting in the queue. You can also reduce your car journey time by carpooling or working from home. Finally, and most importantly, you can just drive Slow down. Every car gets better gas mileage at 50 miles per hour than at 70.
But that gives us an interesting problem to solve: which movement speed saves you the most money?
Here’s the dilemma: if you go fast, you need more gas, which costs more. If you drive slower, it uses less gas, so you’ll save money. But you’ll also be sacrificing time – time you might be spending on the clock at work, income money. There should be an optimum driving speed at which the total cost (gas plus missed work) is minimized. This minimum cost will depend on the fuel efficiency of your car and how much you earn per hour.
Energy efficiency and speed
If you turn on your engine and idle, you’re still using gasoline. (Electric vehicle drivers, this does not apply to you.) At zero miles per hour, your gas mileage will be 0 miles per gallon (mpg), since you haven’t actually gone anywhere. Increasing the speed to 10 mph will also increase your fuel efficiency, as it cannot drop below 0 mpg. But that might not be the best gas mileage. Your car still uses gasoline just to run the engine (and AC and your very loud radio), and you don’t travel very far.
Once you hit much higher speeds, you have other factors that ruin your efficiency. One is all the air your car is now pushing against as it moves. Your engine has to work harder to be able to spin your tires and keep the car moving through this resistance. You can see the effect of air resistance if, while driving on level ground, you shift your car from neutral and take your foot off the brake. The car will start to slow down due to this interaction with the air.
The magnitude of this rearward pushing force, known as aerodynamic drag, increases with increasing speed. You can feel this drag if you stick your hand out the window of a moving car. If the car is going slowly, you hardly feel this force. At highway speeds, that’s pretty significant.