The next time you drive a friend or family member’s car, you’ll probably puzzle over the location of the radio dial, the seat position, and the gearshift. But the most maddening adjustment might be trying to figure out whether the gas tank is on the right or left side of the vehicle. It seems totally random. So why don’t car manufacturers just pick the same side for their fuel tanks?

If this piques your curiosity, you’re not the first. Back in 2014, as Reader's Digest reports, Allstate insurance company writer and blogger Mac Demere investigated the situation and found that there’s no formal regulation for auto manufacturers that dictates which side of the car a gas tank should be placed. It’s completely at the discretion of the car company. The companies, in turn, place the tank in whichever area is easiest for them based on the car’s underbody design. A Nissan spokesperson told Demere that forcing companies to route the gas filler tube to one side every time could inhibit their preferred component layout.

While it may be easier for the automakers, it’s not great for drivers. In a survey conducted by Ford, consumers prefer that the gas tank appear on the left, or driver’s side, of the vehicle because it makes it easier to get close to the gas pumps.

Some companies, however, have their own preferences. If the tank is on the left, it’s easier to route the cable to release the cap. But other carmakers prefer mounting the tank on the right on the premise it’s safer. How? If you need to fill your car’s gas tank roadside from a container, it’s better to be away from the flow of traffic on the driver’s side. Filling up on the right keeps you away from the road.

At one point, manufacturers had this issue licked: They placed the pump directly in the rear center of the vehicle, so you could get to it from either side. But it was eventually determined that placing the fuel tank in the back was a terrible idea in the event of a rear-end collision.

But you don't need to guess where your gas tank is located. Your car’s dashboard should have a fuel gauge. Next to the tiny gas pump image will be an arrow pointing to the side that contains your tank. Just make sure you don’t accidentally fill up with diesel.

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This article was originally published on www.mentalfloss.com as Why Aren't Car Gas Tanks Always on the Same Side?.