Have you ever pulled into a gas station only to realize that your car’s fuel door is on the opposite side from the pump? It may seem random, but there is actually a practical reason behind it. There is no universal rule requiring automakers to place the fuel filler on a specific side. Instead, manufacturers choose the location based on the vehicle’s design, engineering, safety requirements, and manufacturing process.

A car’s underbody contains many important components, including the fuel tank, exhaust system, suspension, wiring, brakes, and structural elements. Engineers have to fit all of these parts together safely and efficiently. The fuel-filler neck also needs a suitable path between the fuel door and the tank, so placing it on one side may make more sense than the other. The location of the exhaust and the need to manage heat can also affect the decision.

Manufacturing considerations can play a role as well. Moving the fuel door may require changes to the bodywork, fuel lines, tank design, or production process, so manufacturers often choose the position that best fits the vehicle’s existing layout. Safety is another important factor, since the fuel system must be protected during crashes while also meeting requirements for fuel containment and emissions control. This is why even vehicles from the same manufacturer can have fuel doors on different sides.

Fortunately, you do not have to remember which side your fuel door is on. Simply look at the fuel-pump symbol on your dashboard. A small triangle or arrow next to the symbol indicates which side of the vehicle the fuel filler is located on. So the next time you arrive at a gas station, check that tiny dashboard arrow before pulling up to the pump—it can save you from stopping on the wrong side.