petrol cap : left or right?

i think almost everyone will come across the following scenario before.

one day, i drove my dad's car to fill up the fuel at petrol station.
when i almost reached, i dunno whether the petrol cap on left or right?

To aviod tis happen, why all the car manufacturer don't make it standardised at one side?
I found the answer from a book named THE ECONOMIC NATURALIST : Why Economics Explains Almost Everything by Robert H Frank.


I try to summarise the answer as follow.
A: If all petrol cap standardised in 1 side, then everybody will hav to queue up during busy time and nobody taking up the pump on the other side. The benefit greatly outweights the cost of occasionally pulling up to the wrong side of the pump.Thus, some petrol cap will be on left, some will be on right.


understand? =P