Unleaded Fuel 87

      I usually fill up my car with gas at Costco. Before putting gas in a car, you can choose from two different types of gases, unleaded and premium, at Costco gas station. Even though I don't know much about car, I just know that my car needs cheaper one, which is unleaded gas.


Costco Gas Station

      While I was giving my husband a ride to the airport, he told me that my car was almost out of gas, so I needed to stop by at a gas station on my way back home. I didn't want to stop by Costco that day, so I went to the nearest gas station from my home. However, at the gas station, I was confused. There were four options. "What does EC Unleaded 87 mean?" "What's difference these four gases?" I usually choose cheaper one at Costco, but I was not sure which one I should choose at this gas station. Eventually, I gave up filling it up there. It was pretty embarrassing for me because I have been living in the U.S for six years now. I should have known about that.

       After that, I asked my husband which one I should have chosen there. He told me that I could choose "87" there. It goes out saying that I didn't know what 87 means. I had never paid attention to these numbers before.

      Today, I searched about the types of fuel. The fuel numbers, 87, 89, and 91, indicate octane rating, which is a standard measure of the performance of a motor fuel. According to Wikipedia, the higher the octane number, the more compression the fuel can withstand before detonating (igniting). In broad terms, fuels with a higher octane rating are used in high performance petrol engines that require higher compression ratios. In contrast, fuels with lower octane numbers (but higher cetane numbers) are ideal for diesel engines, because diesel engines (also referred to as compression-ignition engines) do not compress the fuel but rather compress only air and then inject the fuel into the air heated up by compression, whereas petrol engines (also referred to as gasoline engines) rely on ignition of air and fuel compressed together as a mixture without ignition, which is then ignited at the end of the compression stroke using spark plugs. Therefore, high compressibility of the fuel matters mainly for petrol engines. Use of petrol (gasoline) with lower octane numbers may lead to the problem of engine knocking.

       It's still difficult for me to understand about types of fuel though. I just understand that my small car, Sion xA, needs unleaded gas, 87.

       By the way, in Japan, I have never had problem with choosing types of gases. There are three different gases, レギュラー, ハイオク, and 軽油. レギュラー, regular, fuel is for usual cars such as my Mazda Demio. ハイオク, high octane, fuel is for high performance engine cars. 軽油, light diesel oil, is for heavy-duty trucks and huge buses. Japanese fuel options are much easier to understand, are they?