Your photos, music and documents are irreplaceable. Protect them with Mosey by E m C, the most trusted name and cloud Backup. Back up your files today and save ten percent with promo code. Brain Stuff at Mosey dot com m z y dot com. Welcome to brain Stuff from how Stuff works dot com where smart Happens. Hi. I'm Marshall Brand with today's question what does octane mean? If you've read how car engines work, you know that almost
all cars use four stroke gasoline engines. One of the strokes is the compression stroke, where the engine compresses a cylinder full of air and gas into a much smaller volume before igniting it with the spark plug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of eight to one. The octane rating of gasoline tells you how much the fuel can be compressed before it's spontaneously ignite.
When gas ignites by compression rather than because of the spark plug, it causes knocking in the engine. Knocking can damage and engine, so it's not something you want to have happening. Lower octane gas like regular eight seven octane gasoline can handle the least amount of compression before it starts igniting. The name octane comes from the following fact. When you take crude oil and crack it in a refinery,
you end up getting hydrocarbon chains of different links. These different chain links can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane, and butane. All three of them are hydrocarbons. Methane has just a single carbon atom, Propaine has three carbon atoms chained together, and butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven, and logically octane has eight carbon atoms
chained together. It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane, on the other hand, handles compression very well. You can compress it a lot and nothing happens. Eighty seven octane gasoline is gasoline that contains eight seven percent octane and thirteen percent heptane, or some other combination of fuels that has the same performance as eight thirteen combination of octane
and heptane. It's spontaneously ignites at a given compression level, and it can only be used in engines that do not exceed that compression ratio. Do you have any ideas or suggestions for this podcast? If so, please send me an email at podcast at how stuff works dot com. For more on this and thousands of other topics, go
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