The customer must, be on guard against big-ticket duping that may set him back by a few thousands every year. Here's how it can be done:

Select your petrol pump with care
1. Wherever possible patronise company-owned and company-operated petrol pumps (COCO) that are manned by the oil company officials themselves.

A note of caution here: many petrol stations claim they are COCOs whereas the fact is that they are run by contractors.

One of the best company-owned stations that I know of is an HPCL station behind Hotel Ashok in New Delhi.

The Reliance COCOs are also excellent in respect of delivering the correct quantity of fuel.

2. Another method of identifying stations that don't sell a lot less than one pays for is to go to those stations that are patronised by three-wheelers. This may not be possible in Delhi, Mumbai and Bangalore as all 3-wheelers have shifted to CNG, but this rule-of-thumb can be applied to those cities where 3-wheelers still run on petrol (Pune, Hyderabad, etc.). These auto rickshaw drivers check mileage after every refill and use their own methods like dipping a foot-ruler into the tank to know if the pump has delivered the correct quantity or not. And they are always right in their assessment!

3. It is best to patronise stations, which have the newest pumps like the multi-product dispensers (MPDs) installed to service customers. MPDs are believed to be quite tamper-proof and hence they will deliver correct quantity of petrol. I have even found that many dealers complain about MPDs delivering excess quantities due to the voltage fluctuations!

Many high selling stations in big cities are equipped with MPDs. I can say from experience that the old mechanical pumps can be easily manipulated to sell short.

Often check your car's mileage
1. One good way to know if your regular filling station is delivering short or not is to top up your tank. It is dangerous to top up the tank to the brim. The best method to top up the tank is to get the fill-up from a pump that has an auto-cut-off nozzle.

The moment the nozzle cuts off the fuel supply, stop filling up at that point. Note your car's odometer reading. Let's suppose that the odometer reading is 8,000 km. After a few days, come back to the same pump and again fill up using the auto-cut-off nozzle. Note the odometer reading again. If the odometer reading reads 8500 km and on the second turn you bought 30 litres petrol before the pump nozzle cut off then your car has given a per litre mileage of (8,500-8,000)/ 30 = 16.6 km per litre.

2. You should repeat the same exercise at other stations. The station that gives your car the best mileage per litre is the best station for you. In fact, this exercise should be carried out as many times as possible to eliminate any inaccuracies that might creep into the results due to varying traffic congestions on different routes at different times.

Be alert when you enter a petrol pump

1. Always ensure that before the fuelling process is started the pump board display reading is set at ZERO.

What might have happened in Joseph's case is that the customer who was serviced at the pump before Joseph bought 15 litres of petrol and when Joseph's turn came, the salesman started filling up his car tank with the pump display showing 15 litres. He stopped after the pump display showed 30 litres. Joseph thought that he received 15 litres, but in reality he got only 15 litres.

2. Come out of your car while the salesman fills up your tank. Many salesmen at some petrol pumps indulge in sharp practice. I have known a station in Delhi, where the moment you position your car near the pump island, a salesman will come near you and engage you in polite conversation while his colleague at the other end would pour some of the petrol not into your tank but in a container hidden from you!

It is therefore best to come out of your car and stand near the point of sale to ensure that you are not at the receiving end of any such sharp practice.

3. Instruct the salesman to deliver the fuel slowly. Unbelievable as it may seem, the fact is that several pumps (even the swanky electronic Z-line pumps) are adjusted in such a manner that if the fuel is dispensed at a fast pace, the quantity actually dispensed is less than what you pay for based upon the display reading on the pump board. It is advisable that the salesman is instructed to deliver petrol at a slow pace.

You may end up getting more fuel than you pay for, much to the chagrin of the canny dealer. I would add here that not all dealers have perfected this manipulation of pumps and that only a few dealers practice this 'art.'

Lodge a complaint if you feel you have been short-changed

1. Oil companies are quite swift in attending to the complaints that they receive in writing. It is no use asking the salesmen for the complaint register. He will always say that it is locked up in the cupboard or may cook any other excuse. It is better to lodge the complaint on the Web site of the oil majors or send a written complaint to their office.

The phone numbers and the office address are prominently displayed at the station and the complaints are quickly attended to.

2. Being informed about your rights helps. It is your right to know if the quantity being dispensed to you is correct and it's the dealer's duty to provide all necessary assistance to you. Consumer rights and the duties of the oil companies are contained in the Citizen's Charter issued by the oil companies and endorsed by the Union petroleum ministry.

Each station is required to keep a five-litre calibrated measure (certified by the Weights and Measures Department) and you can demand that the measure be filled up in your presence to let you know the if the pump is dispensing accurately or not.

I would even suggest that in case you feel strongly about something, please call up the field manager of the respective oil company and fix an appointment with him at the petrol station. He will personally enlighten you about the various checks for assessing the quality of the product, like the simple density test. He may even agree to draw samples of the product and will deliver it to the ISO accredited laboratory. He will also deliver to you the test results. Oil companies have changed over the years and the field managers deployed are amongst the best officers working for the oil PSUs.

So next time you enter a petrol station, be alert so that you are not duped.

Also don't forget to tip the salesman if you are happy. These guys are poorly paid and if we all leave some small change for them, they may even give up this sharp practice.