[srishiva]

If you fill a 1 litre can, you do get 1 litre!

The sensor is based on some air flow if I remember correctly.

[a4anurag]

Originally Posted by foby.sebastian

But the returned petrol has already passed through the meter, meaning you are donating the petrol back to SHELL/CALTEX/MOBIL/ PETRONAS

Originally Posted by rr_zen

I was wondering if I should get my fuel gauge checked and now I bump into this thread.

Originally Posted by Sahil

It is unlikely that there will ever be clarity on this issue as we won't have an concrete evidence unless someone inspects a few pumps.

Originally Posted by srishiva

The sensor is based on some air flow if I remember correctly.

SOURCE: http://auto.howstuffworks.com/fuel-e...-full-tank.htm

How does a gas pump know when my tank is full?

This mechanism has been around for a long time, so it is safe to say there is not a miniature camera inside the nozzle hooked to a microprocessor. It's purely mechanical -- and ingenious. Near the tip of the nozzle is a small hole, and a small pipe leads back from the hole into the handle.

Suction is applied to this pipe using a venturi. When the tank is not full, air is being drawn through the hole by the vacuum, and the air flows easily. When fuel in the tank rises high enough to block the hole, a mechanical linkage in the handle senses the change in suction and flips the nozzle off.

Here's a way to think about it -- you've got a small pipe with suction being applied at one end and air flowing through the pipe easily. If you stick the free end of the pipe in a glass of water, much more suction is needed, so a vacuum develops in the middle of the pipe. That vacuum can be used to flip a lever that cuts off the nozzle. The next time you fill up your tank, look for this hole either on the inside or the outside of the tip.

Anurag.