Inaccurate petrol pumps?

vikingaero

I'm not sure how you can feel 11p worth of fuel being pumped? Or see " a dial" as Asda unattended self serve pumps are wholly digital. I imagine most pumps would be set to deliver minutely over the amount pumped to satisfy Weights & Measures.

facade

MileMartin wrote: »

Was wondering how I managed to get almost 51 litres into a Polo yesterday when the handbook clearly shows a 45 litre capacity?

there is an airspace above the fuel, that you normaly can't fill. If you rock the car, or are on a slope, you can usually get fuel into it.

It is there, because, despite what the naysayers think, petrol expands a lot, and worse, vaporises readily.
Modern fuel systems are sealed, with a breather pipe going to a charcoal filter in the engine bay. The breather pipe ends in this airspace.

When fuel vaporises, there is a pressure relief valve in the breather line that allows the vapour into the filter, which absorbs it.
Next time you start the car, fresh air is drawn through the charcoal into the engine to clean it.

If you over fill the tank, liquid fuel goes along that line and fills the charcoal filter, then leaks out under the bonnet. Then when you start the engine, it runs badly for a few seconds as the neat fuel is sucked into the engine.

As you use the fuel, air goes the other way along the breather pipe.