Fuel doors aren’t always on the same side because there is no industry-wide rule requiring them to be. Automakers choose the location based on the vehicle’s design, engineering, safety, and manufacturing needs, with the goal of fitting everything together efficiently.

Under a car, engineers have to make room for the fuel tank, exhaust system, suspension, wiring, brakes, and structural components. The fuel-filler neck also needs a practical route from the fuel door to the tank, while exhaust placement and heat management can influence which side works best.

Manufacturing and safety also play a role. Moving the fuel door could require changes to the body, fuel lines, or production process, while the fuel system must be positioned to meet safety and emissions requirements. That’s why even vehicles from the same manufacturer can have fuel doors on different sides.

The good news is that you don’t have to remember which side your car uses. Simply check the fuel-pump symbol on the dashboard: a small triangle or arrow next to it shows the location of the fuel filler. Next time you pull into a gas station, that tiny indicator can save you from choosing the wrong side.