I do not think anyone who really likes to fill up the gas tank. It feels like you’re just standing around when you can get somewhere. If you get gas in your hands or shoes, you will smell like that all day. And on top of that, you actually have to pay for it. With gas prices above $4 a gallon (which can go as high as $6 in some states), we’re all too painful to realize that gas doesn’t come cheap.
Of course, there are many things you can do to spend less at the pump. US Department of Energy there are some tips to help you save fuel, including getting rid of the roof cargo and leftovers in your trunk, using cruise control, and even turning off the engine while waiting to get to the driveway. You can also reduce your driving by carpooling or working from home. Finally — and this is important — you can drive Slower. Each car gets better gas mileage at 50 mph than it does at 70.
But that leaves us with an interesting problem to solve: Which commute rate saves you the most money?
Here’s the dilemma: If you drive fast, you’ll spend more gas, more money. If you drive slower, it will use less gas, so you will save money. But you’ll also sacrifice time — the time you might spend on the clock at work, make money money. Some optimal driving speed is required to minimize total costs (gasoline plus missed work). This minimum cost will depend on your car’s fuel efficiency and how much you earn per hour.
Fuel efficiency and speed
If you start the engine and just idling there, you’re still using gas. (Tram driver, this doesn’t apply to you.) At zero miles per hour, your gas mileage will be 0 miles per gallon (mpg), because you’re really not going anywhere. Increasing your speed to 10 mph will also increase your fuel efficiency, as it can’t go lower than 0 mpg. But it may not be the best gas mileage. Your car is still using gas just to run the engine (and your huge AC and radio), and you haven’t gotten very far.
When you get to much higher speeds, you have a number of other factors that damage your efficiency. One is all the air your vehicle is currently resisting as it moves. Your engine has to work harder to turn your tires and keep moving the car forward despite this drag. You can see the effect of air resistance if, while driving on the ground, you switch the vehicle from drive to neutral and take your foot off the brake. The vehicle will begin to decelerate due to this interaction with the air.
The magnitude of this reverse thrust, known as air resistance, increases as speed increases. You can feel this drag if you stick your hand out the window of a moving car. If the car is moving slowly, you can barely feel the force. At highway speeds, it is quite remarkable.
