Keep the tank topped up
H. Kishie Singh
driving to Delhi on N.H. 1, when you come down over the Ambala
flyover, the Indian Oil depot is on the left. The huge
reservoirs can be seen from the flyover and in case you missed
them, you will surely see oil tankers, a hundred or more,
waiting to fill up. They are there in the evening; they fill up
at night, when it is cool, and by early morning, they are gone.
Why do they
refuel in the cool of the night? Because cool petrol is dense;
when the temperature rises, petrol expands. So a litre is not
really a litre. In the petroleum business, the specific gravity
and temperature of the fuel, be it petrol, diesel, LPG or
ethanol, play an important role. A one-degree rise in
temperature makes a big difference. It is for this reason that
you are advised to refuel either in the morning or evening when
the temperatures are cool. During summers when day temperatures
can be close to 40 degree C, a fair amount will be lost to
evaporation, in addition to the fact that expansion will have
shrunk the litre. Money lost.
has self-service petrol stations. This is where you can save
fuel and money while refuelling. The lever in the nozzle has
three speeds for delivering the fuel — fast, medium and slow.
Select the slow mode, thereby minimising the vapour that is
created while pumping. Most attendants select fast. They want to
refuel your car as fast as possible because others are waiting.
All nozzles have a return hose to trap the vapour.
If you pump at
a fast rate, some of the fuel, especially petrol, that goes into
your tank becomes vapour. Those vapours are then sucked into the
underground tank. So you are getting a "smaller" litre
and less for your money. The petrol station benefits from this;
hence the attendants pump at a high speed.
There is a
strange syndrome of refuelling in our country. People usually
buy 10 or 15 litres at a time. It is a waste of time and money.
Your fuel bill at the end of the month will be the same.
recommended that you keep your tank full at all times. Refuel
when the tank is half full. The reason is simple. In a half-full
tank, as opposed to an almost empty tank, there is less air
occupying the empty space. The more the air, the greater the
evaporation. Informatively, the underground tanks have an
internal floating roof, or they are supposed to have this false
roof. This false roof serves as zero clearance between the
atmosphere and the petrol; so it minimises evaporation.
Petroleum companies safeguard themselves against evaporation
loss. You can do the same; keep the tank topped up.
recommendation. Many times you go to refuel, and there is a
tanker discharging fuel into the underground tanks. Do not
refuel! With thousands of litres gushing into the reservoirs,
the petrol in the underground tanks is being stirred up. All the
grit at the bottom of the tank is floating around and the fuel
you take on could have some grit in it.
This is another
very good reason to refuel in the morning. The tanker delivered
fuel during the day, and if you refuel in the morning, the grit
has had 8-10 hours to allow the grit to settle down. You will
get cleaner fuel and a full litre for your money.
There is also
an auto-cut facility on the hoses. There is a sensor in the
nozzle, which senses that the tank is full and stops delivery
automatically. Reason: it leaves a little space for the fuel to
expand. Attendants will then pump in a few extra points to round
off the figure of the payment. No good. It is a common sight to
see the drivers of sarkari Ambassadors rocking the car
till the petrol is full to the brim. A very foolish move. He
would then drive the sahib to work and the car would be
parked for hours in possibly 40 degree C heat. The petrol will
expand and spill out. A waste of petrol plus a potential fire
hazard that could blow everyone sky high, and all for, maybe, an
additional quarter litre of petrol!