When filling up the tank, do you ever stop while holding onto the pump and think about what exactly is going into your tank? “What do those numbers mean,” you think, “what is ‘unleaded’?” Well, dear reader, today we shall discover exactly what is meant by the crude hieroglyphics and numerals on gas station pumps.

First of all, the SCIENCE! I am not good at science, so I will try to explain this in easy terms, because the easier it is to explain the harder it is for me to get it wrong. Okay. So, when gasoline is refined from oil, molecules called hydrocarbons are left in the gasoline. Hydrocarbons like to spontaneously combust, often before we’d like them to when it comes to thinking about how engines work. This used to create a phenomenon known as an “engine knock” in the past, which was very annoying to everyone because it was literally just your car’s engine yelling at you in the most obnoxious way possible. However, a certain hydrocarbon known as isooctane (or as we call it, octane) is much better at combusting when we would like it to, so this is a molecule we want to have more of in our gasoline. The numbers on the pumps indicate the octane level of the gasoline that comes out of that particular nozzle thing.

At this point, you might have had the thought, “why am I not using higher octane gasoline?” The answer to this is simple: because you do not need to. You would know if you needed higher octane gas in your engine because your vehicle would say so, either on the dash next to the gas gauge or inside your gas cap or in your owner’s manual. Only higher-performance engines really need the high octane gas, because other engines have been made specifically to work with the lower-octane stuff. Don’t worry. Using higher octane gas in a normal engine is literally just a waste of money.

So, what is the deal with the “unleaded” nonsense? All gasoline is unleaded, right? Answer: yes, but it took until the 1990s for that to happen. In the 1920s, car scientists (is that a real thing? I am making it up right now, so it is now a real thing) figured out that a good cheap way of increasing the octane level of gasoline is by adding tetraethyl lead to it. Of course, this will kill you slowly and painfully but hey! It’ll keep the cost of gasoline down. So they were totally on board for that for 70-something years, until the anger of the dying populace became too strong and lead was outlawed from gasoline in the late 1990s.

And there you have it! If you want to not think about this as often, consider purchasing a new hybrid vehicle! Fuel efficiency is in.