Supposedly going faster uses more fuel. But your getting to the place quicker. Shouldn’t you just be using the same amount of fuel as if you were driving slower and getting there later?
In: Chemistry
The formula for drag varies with the SQUARE of your speed.
So, if you are going 10% faster, 1.1 x 1.1 = 1.21
The drag going 10% faster is 20% higher than it was at the slower speed. Assuming all else was equal, you will need to use 21% more energy to go 66 mph than you would 60 mph. To go 75 mph would take (75/60)^2 = 1.56 times the energy needed to go 60 mph.
Not only does going faster use more fuel, it uses that fuel less efficiently. Wind resistance increases with the square of speed, if you go twice as fast, all things being equal, you have to burn more than twice as much fuel.
Also, engines have a sweet spot, and rpm range where they work most efficiently. If you car isn’t geared to go 100 mph, then your engine will be operating outside of that sweet spot, wasting additional fuel.
Best way to do it is speed up fast.. Then go to neutral and coast for a while then speed up and repeat.
Here is an easier comparison if you will allow some leniency. What is easier for you? Running up a flight of stairs as fast as possible or casually walking up them? Both are the same distance but one requires more “fuel”
Also, you need to consider efficiency. Your vehicle may be more efficient in fuel economy at 45 miles per hour than it is at 90 miles per hour.
The faster a vehicle travels, the higher the air resistance and that resistance goes up much faster the faster you go. IE doubling your speed doesn’t double the air resistance, it’s more like quadrupling it.
The optimum speed for best range and efficiency will vary with a vehicle depending mostly on it’s aerodynamics. Generally the more slippery it is through the air, the higher it’s most efficient speed.
First of all, you don’t need any fuel to keep your vehicle at certain speed. You need fuel to gain acceleration. You use acceleration to get your car to a certain speed. If you travel with your car on earth, there are a lot of things, which try to slow down your car, such as friction or air. You also need acceleration to surpass the opposing forces. These forces can be generalized, so that you can calculate the required acceleration, which allows you to stay at the same speed.
Car engine is a complicated thing. Engines are designed to be the most efficient at certain acceleration or speed for each gear. You wouldn’t want to go in details, but know, that things that you wouldn’t imagine are taken into account (such as the proportion of oxygen to other gases in atmosphere) in order to calculate the designed efficiency. With that said, to be the most efficient, you need to use the most efficient speed at the most efficient gear (which usually is the highest gear). Going too slow, or too fast is inefficient by design.
Fuel consumption is linked mainly to throttle position and (pseudo) engine revolutions (because you need enough to keep banging the pistons back up at that speed).
If you’re in top gear, low revs, you’re more fuel efficient than one gear down, high-revs.
You can get further on a tank of fuel at 50mph than you would at 80mph or even 100mph or at 30mph in a low gear. When they measure fuel efficiency, it’s always top gear, lowest possible revs (often just literally whatever tickover-without-stalling is).
Fuel consumption doesn’t really care what gear you’re in… you’ll burn as much fuel per second at a fixed rev. But obviously if you wanted to go FAR you’ll need to be in a higher gear at that fixed rev, and higher gears will therefore get you further before the fuel runs out.
No, because fuel consumption is measured per mile traveled, not time elapsed. If you get 20mpg instead of 25mpg, only mileage traveled matters and not that it took you 50 minutes instead of an hour.
Things aren’t always linearly proportional.
Example from Wikipedia: https://en.wikipedia.org/wiki/Atmospheric_entry
> convective heating is proportional to the velocity cubed, while radiative heating is proportional to the velocity exponentiated to the eighth power
So if you go twice as fast, you don’t just generate twice the heat. Instead, you’ll generate 8 times as much convective heat and 256 times the radiative heat compared to if you just went your “normal speed”. It’s not always 1:1.
Most commonly, the burning is expressed in [L/100km]. So driving at 60km/h will make you use up 2L of fuel after 100km. Driving at 140km/h will use up 8L after 100km. It doesn’t go up proportionately because of wind resistance and the suboptimal work of the engine.
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