# I have a Fuel Question?

how many liters of Gasoline do you need to run a car 1km? how much pollution does it make?

how many liters of Diesel do you need to run a car 1km? how much pollution does it make?

how many liters of Hydrogen do you need to run a car 1km?

how much electrical energy do you need to run a car 1 km?

ALL ON AVERAGE, DOES NOT NEED TO BE 100% ON. dont care about engine size olny average thanks......

Relevance

Didn't you just have a fuel question?: http://answers.yahoo.com/question/index;_ylt=AjOnJ... (I would not want to see you get in trouble asking the same question multiple times.)

Gasoline, diesel, hydrogen and electricity are all carriers of energy. You could compare the energy directly if the process to convert it was the same in each case and subject to the same efficiency of conversion. Here is a table of comparison of energy in each fuel: http://en.wikipedia.org/wiki/Gasoline_gallon_equiv... (sorry it is in English measure but you can easily find conversion calculators on the web.)

Unfortunately not all fuels are used with equal efficiency. Some cars with internal combustion engines are light and efficient. Others might be very heavy vehicles and rather inefficient (like a tank.) But an internal combustion engine is a heat engine and therefore subject to the laws of thermodynamics. As such we say that the maximum theoretical efficiency for a gas engine is about 30% and for a diesel due to its higher compression ratio is about 40%. By the time this translates to actual movement the percentage might be lower than 15%. It depends upon how much work the engine has to do that is not strictly related to movement. A tank has to move a lot more weight around than a Smart 4 2.

Then again you can compare the fuel usage of a hydrogen fuel cell electric car and a battery electric car to the internal combustion engines but you have to know what you want to compare as efficiency is always based upon a desired goal. In this case movement and not necessarily the heater or air conditioner blasting. Electric vehicles are not heat engines and are not subject in the same way to the laws of thermodynamics for efficiency. An electric motor can be 90 to 95% efficient. With regenerative braking these vehicles may reach efficiencies of around 85 to 90%. This is a good thing for their overall distance traveled on a tankful because it means that they have to carry far less energy to go a reasonable distance. Battery electric vehicles usually have around the equivalent of around one or two gallons of gasoline stored on board.

But the above understanding presents a problem with trying to determine an "average" vehicle. We can say that our "average" internal combustion engine car will get 20 miles to the gallon. But it is unfair to hold the electrics to the same inefficient standard. Their engines are much better at turning energy to motion. But based upon the 15% and 85% analysis we can come up with an "average" equivalent standard for an electric vehicle.

If a gasoline vehicle used 100% of its energy efficiently the "average" mileage would be (20/15 : x/100 = 2000/15) or 133.34 miles. For an "average" electric vehicle the mileage would then be 133.34/100 : x/85 = 113.34 miles based upon drive train efficiency.

So this means that it takes the same energy to drive an ICE gasoline car 20 miles as it would to drive an electric 113.34 miles. Or, going back to the chart, it takes about 114,000 BTU in one gallon of gasoline to take the car 20 miles if it has an ICE but the same number can be converted to 33.4 KWh (and this will drive a car with an electric motor 113.4 miles.)

All that is left is to convert back to metrics and change the scale. 20 mi. = 32.1868 km from: http://www.metric-conversions.org/length/miles-to-... 113.4 mi. = 182.499 km 1 gal(US Liq) = 3.78541 L So 3.78541 L will take the "average" car 32.1868 km which means that our hypothetical ICE car needs 3.78541/32.1868 : x/1 = .1176 L to drive 1km while the electric version needs the equivalent of 1 gallon to drive 182.499 km or 3.7854 L to drive 182.499 km. This could be converted to the equivalent of .0207 L to drive 1 km. Expressed in Watts this would be 33.4 KWh for 182.499 km or .1830 kWh to go 1 km. 33.4 kWh is equal to 120199999.99999998 Joules: http://www.mhi-inc.com/Converter/watt_calculator.h... Therefore the end result would be 658633.745938 joules for 1 km.

Diesel engines are slightly more efficient than the gasoline version and the fuel has slightly more energy in it (129,500 BTU/gallon) so your answer would be slightly less fuel. Hydrogen has far less energy and it depends upon how you are using the fuel. If you burn it you are subject to the inefficiencies of the ICE engine. If you use a fuel cell to produce electricity your efficiency may be around 50%. This answer is already too long so I will leave you to fill in the last two calculations.

Thanks for an interesting question.

• Anonymous