Did you know that you can tell which side your petrol filler cap is just by looking at your fuel gauge?  Not a lot of people know that! On most cars there is a small arrow next to the petrol fillter symbol, and whichever side it is on indicates the side to use for filling up your car/ Very handy if you have a hire car, or perhaps are just forgetful.
Here's a link to an example image.
I'd be interested to know if your car does or doesn't have this handy little feature