How Much More Petrol Does A Car Use Travelling At 20mph Than 30mph?

Question

Anyone know?

Answer 1

A drag coefficient means that no matter what the number, if you double the speed you have to quad the HP requirement so lets say that a car takes 15HP to run at 60 mph just in fuel it takes 3 gallon per hr. If you re-gear and reset up the car for the optimum fuel efficiency it will take .375 gallon per hr at 30mph due to the Drag on the car. After you finish making up for the cars drag you also have to add the actual work being don. Up hills and into the wind or with the wind are all factors. That is why during the gas crunch of the 1970s the Federal government pushed for the 55 speed limit…. It was to save fuel. Generally speaking a gas engine will produce on the shaft 2.3 Hp for one hr on one gallon of gas. The maximum HP achievable on a normally aspirated engine per cubic inch is 2.2 HP. So for review unless you start breaking the laws of physics it takes less energy to travel at 30 for 10 miles than it does to travel at 60 for 10 miles.
Cars get better gas milage on the highway becasue they are cruising ..... not starting and stopping, or idelling at red lights

Answer 2

Probably the same, since you'd need to be in a lower gear. Most cars will do 30mph at about 1500-1800rpm in 4th gear, but wouldn't hold 20mph in that gear, so you'd need 3rd, but hey, screw the environment, it still means we use the same amount of petrol, and therefore pay the same tax, to go slower!

Answer 3

the same cause at 25mph ur automatic gear would change to a bigger gear instead of the smaller gear but if ur driving 20 mph and 45 mph then yea u need more gas cause the winds pressure .
try going 100 mph on a highway for like good 5 minutes adn see how ur gas gauge would go down cause u need more power to push that car thru trhe air .
when they test the car for epa milleage
for the city it's 5 stop light and driving at 45 mph
for highway it's exit and 3 entrance a mile in between and top speed at 65 mph

Answer 4

Most cars will use more petrol, as most cars are geared to be economical at around 50-70 mph, depending on aerodynamics and engine torque, most engines are most efficient below 3500 rpm, above this the internal resistance makes them less efficient

How did road safety get in to the answers????

Answer 5

Consumption will entirely depend on the car.

It is quite possible that some cars will use more petrol/emit more fumes while others use less/emit fewer fumes.

It will depend on the type and size of engine, the style of driving and on the gearing of the car.

Answer 6

Probably less as whilst driving in a built up area it's all start stop driving anyway.

My own worries are that the slower the car the quieter it gets, as tyre noise decreases.

I'd rather see them bring in the scandinavian 'lights on at all times' approach.

Answer 7

would you complain if it saved a childs life?

Would you really prefer cars to drive at 30mph rather than 20 when children are around?

I know which i would prefer when my son is playing outside

Answer 8

depends on the type and size of engine and what gear you use.

Answer 9

The same............