why is methane not used for car fuels but instead octane?

Answer 1

the energy provided from the combustion of octane is greater than that of methane. This will result in more energy/unit space. If you were to power a car on methane, you would need to fill up more frequently or have a much larger gas tank

Answer 2

It has to do with the physical state (solid, liquid, or gas) that methane and octane are in at room temperature and pressure. Methane, also known as "natural gas" is a gas at room temp. and press. while octane (gasoline) is liquid. The individual molecules are spread really far apart in gases, while they actually are touching in liquids and solids. In other words, the energy contained in the methane is spread out over a large volume because it's a gas while the energy in the octane is concentrated because it's a liquid. To put it in perspective, if you want to carry the amount of energy that is in just 1 gallon of octane, you'd have to have a tank of methane that is practically bigger than the entire car. One way around this is to compress the natural gas so that the molecules are closer together and take up less space, thus concentrating the energy in them and allowing the use of a smaller fuel tank. There are vehicles on the road today that use compressed natural gas, but they are mostly commercial vehicles that are part of a fleet. The biggest problem with using compressed natural gas is that the compressed methane is harder to handle because it's under pressure. A compressed methane tank has to have extra protection so it doesn't rupture in a collision. Special service stations are needed to fill up cars with compressed natural gas, and so on. In the furture, it may be possible for people to use a compressor to compress the natural gas from their house and power their cars with that. Hope this helps.

Answer 3

It would be difficult to carry enough methane to travel a respectable distance before having to fill up again, because it's a gas. It would also require a compressed (and therefore dangerous in crashes) gas cylinder in the car.