A couple of months ago a Steve Sutcliffe blog on this site went viral and popped up in the national press.

Sutcliffe quoted his mother-in-law, who had heard of a sure fire way of working out what side of the car the fuel filler resided.

Read Steve Sutcliffe's original blog on fuel filler caps

As it happened, her sure-fire rule (that the fuel gauge graphic gave the clue) was not quite as sure fire as it first appeared.

Well, I haven’t got a sure fire way knowing either, but I think I can explain why the filler cap is where it is on your car.

When a car is designed, it usually designed from either a left-hand or right-hand drive point of view. Although it must date back decades, the general rule seems to be that a car’s drivetrain is engineered so the exhaust exits on the opposite side to the pavement.

So a car designed in a LHD country, such as a Renault Megane, would normally be driven on the right, so the exhaust will exit on the left rear corner of the car. Decades ago exhaust gases were rather more pungent, so that layout makes sense.