Type the density at 15 °C printed on the invoice, then your hydrometer reading and its temperature. The calculator works out your density at 15 °C by Table 53B and the difference. The Marketing Discipline Guidelines allow ±3.0 kg/m³.
Marketing Discipline Guidelines 2024, clause 1.2 (iv): density at 15 °C by ASTM Table 53B, within ±3.0 kg/m³ of the invoice density.
The rule
Clause 1.2 (iv) of the Marketing Discipline Guidelines 2024 reads: the dealer is “to check that the Density of product @ 15°C using ASTM Tables (53B) is within +/- 3.0 Kg/M3 as compared with the Invoice density for ascertaining quality of product.”
Why density gives adulteration away
Petrol and diesel each sit in a narrow density band. Kerosene, solvents or naphtha mixed in move the density. A drop or rise of more than 3 kg/m³ against the depot’s own figure is the first sign that what is in the tanker is not what was loaded.
Write it down
Record each compartment in the density register (Annexure 1 of the MDG): the date, the tank truck receipt density by compartment, the invoice density, and, after decanting and dispensing 50 litres, the density of the mixed product in your tank.
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 difference is more than 3 kg/m³?
Do not decant. Take a fresh sample and read again. If it is still outside, contact the supply location or your area officer for instructions, as clause 1.2 (ix) of the MDG says.
Do I check every compartment?
Yes. The MDG asks for about 20 litres to be drained from the manifold of each compartment into a clear glass jar, and each compartment to be checked and recorded on its own.