Samples are kept at three points so any fuel can be traced to its source: the depot keeps daily samples, the dealer keeps a sealed sample from every tanker, and oil company officials draw samples from the pump nozzles. The dealer keeps the tank lorry samples of the last two loads for each tank.
Why three tiers
MDG 2024 chapter 2 states the aim: to ensure that the petrol and diesel sold at an outlet is the same product its oil company supplied. Samples kept at each step let a dispute be settled by testing what was really loaded and delivered.
Tier 1: at the supply location
Every day the depot keeps at least 4 × 1 litre of petrol and 2 × 1 litre of diesel from the loading point, and again after switching storage tanks. Samples are labelled and kept for at least 30 days. The invoice states the density at 15 °C, the loading point, the storage tank and the time the lorry left.
Tier 2: the dealer’s tank lorry sample
After the density check passes, and after draining at least 20 litres from each compartment:
- Draw 2 × 1 litre of petrol and/or 1 × 1 litre of diesel as bottom samples, in proportion to each compartment’s quantity.
- Rinse the empty aluminium containers with the same product first.
- Seal and label them before unloading. The dealer and the driver both sign the label.
- Mark the storage tank the product went into, if there is more than one.
- Keep the samples of the last two loads for each tank.
The transporter may take a second set, paying for it and a deposit of ₹300 per container.
Tier 3: the oil company’s samples
Officials, mobile labs and authorised agencies draw samples from the nozzles of every tank. Random sampling covers at least 2% of the network every month, and samples are also drawn after a density failure, a filter paper failure, a stock variation beyond the limit, or a complaint. For petrol, six 1 litre samples come from each tank: two for the dealer, two for the office and two for the laboratory. Officials bring their own containers and pay for the fuel with a cash memo.
Figures here are for reference. Your oil company’s certified calibration chart, approved instruments and the Marketing Discipline Guidelines always prevail.
Questions
What if the tank lorry driver refuses to sign the sample label?
Do not decant. MDG 2024 says to contact the supply location or the sales officer.
How many samples does an inspector take?
For petrol, six 1 litre samples from each tank: two stay with the dealer, two at the oil company's office, and two go to the laboratory.