To make it clearer, instead of the 10 litres that the meter indicates the motorists might only be getting about nine litres. While the mileage may eventually reveal that they been shortchanged, the motorist has no way of proving the case. Surprise raids on various petrol pumps in the Capital by the Weights and Measures Department of the Delhi Government resulted in pumping units at 10 petrol pumps being sealed. Like numerous earlier cases, these were found to be supplying less petrol than the meter reading indicated.

The petrol pumps failed a simple test. The officials had a five-litre can which was filled at the petrol pumps. Though the meter showed a reading of five litres, the can was not filled up. Following this the officials challaned the petrol pump owner and sealed the faulty unit. The petrol pump ownersface action under the Weights and Measures Act which usually involves the payment of a penalty of around Rs 5,000. On an average the petrol pump had fallen short of the meter reading by 100 ml to 500 ml per five litres. To a motorist this would mean a loss of Rs 2.40 to Rs 12 per five litres. A petrol pump in the Capital sells anything between 10,000 litres to 20,000 litres per day, this works out to a massive margin for the dealers.

A senior official explains the modus operandi, ``Firstly, the petrol meters run on electricity, whose voltage decides their speed. A meter might run faster and record an incorrect reading if the voltage is high. Secondly, a petrol pump might have two tampered meters and four normal ones. A motorist might be led to the tampered meters by the staff very innocuously. Thirdly, the pipe which leads from the pump might hold a litre at the end of the filling which the meter might show but need not be delivered to the vehicle.'' But, according to a senior member of the executivecommittee of the Petrol Dealers' Association, ``The Weights and Measures Department along with the company which supplies us the fuel, seals the pump in a tamper-proof manner. If the seal is intact then the officials have no business to challan the petrol pump owners.''

How, then, does one account for the variation in the meters? ``Like every other machine even a pump undergoes changes over a period of time,'' the executive committee member says. Moreover, ``during summer about 15 ml of petrol is lost in evaporation. While the petrol is carried in tankers at 45 degrees Celsius, we put it in underground tanks at a temperature of 25 degrees Celsius. That leads of a condensation of 1.2 litres per degree per 1,000 litres.''