What dictates which side your car’s petrol cap is on?

If you own more than one car or are borrowing or renting one, you’ve probably pulled up to the petrol bowser on the wrong side of the vehicle at least once.

RELATED: Does your car actually need premium petrol?

You then have to decide between moving the car to another bowser or stretching the nozzle and hose across to the other side of the car.

You might even think to yourself, “Why don’t they just put these all on the same side?”. The answer is complicated and, to be honest, a little difficult to pin down.

So, what actually dictates which side of the car the petrol cap sits on? Here's what we know...

Common sense would say that if every car had its fuel door on the same side, it would cause traffic chaos at the petrol stations.

However, this isn't the reason manufacturers put their petrol doors on opposite sides of the car.

Rather, the petrol cap's location can be dictated by a number of factors, including which country the car was built in/for, the design of the car, and the relevant safety requirements.

Most cars that are built for a right-hand-drive market, i.e. Australia, the United Kingdom or Asia, will likely have the petrol cap on the passenger side.

This allows for an easier fill, allowing the driver to get out of the car without the need to squeeze out between the petrol bowser and door.

Another reason the fuel cap is located on the opposite side to the driver is to allow for a safer emergency refill on the shoulder of the road if you were to run out of fuel, so your back is not facing the passing traffic.

Asian markets often favour the petrol door on the passenger side for the reasons listed above. This is seen with the top 10 best-selling ICE cars in Australia all being constructed in Asia. Out of those 10 cars, eight have a petrol cap on the passenger side.

The only exceptions are the MG ZS and Mitsubishi Outlander, both of which are built in Asia and have petrol caps on the right-hand side of the vehicle.

Meanwhile, when we take a look at European brands like BMW, Mercedes-Benz and Audi, you will more likely see the fuel cap on the driver’s side since these models were built to predominately be sold within a left-hand-drive market, where they would sit on the passenger side of a left-hand-drive model.

This brings us to the next variable on petrol door placement, which is the car's overall design.

The majority of petrol tanks on brand-new vehicles sit in the middle and underneath the car. With things like differentials, suspension components and brake lines getting in the way, the manufacturer will run the fuel neck up the side of the car where it can most easily sit.

A big deciding factor in where the fuel neck runs is how the exhaust is managed. If your exhaust pipe runs down the passenger side of the car, then your fuel door will most likely sit on the driver’s side, and vice versa.

Some older vehicles, such as the original Mini and the Ford Escort, have their petrol tanks mounted off to the side in the rear quarter panel. Although this is an issue for a side impact, if you were to be T-boned, it would create a fire hazard.

A logical way to stop the shuffle at the petrol station when you pull up on the wrong side is to put the petrol door in the middle and at the back of the car.

Some car models, predominately American cars, used to have the fuel filler in the middle at the rear of the car. However, the innovation, and later mandatory nature, of crumple zones in cars made this a fire hazard.

Even before the invention of crumple zones, it was still possible to snap the fuel neck off in a simple fender-bender, sending your highly flammable fuel spilling everywhere.

To easily figure out which side of the car your fuel door is located, your fuel gauge will have a helpful little arrow pointing to the side that your fuel door will be on.

Some newer model cars with digital displays also show a diagram pointing to the location of the fuel door, so you don’t have to guess.