Why do fuel volumes differ at 29.5 C and 15 C, and which should I use?
Oil expands when warm, so the same tonne fills more litres at 29.5 C than at 15 C. PPAC publishes correction factors from 0.9830 for petrol to 0.9899 for furnace oil. Use whatever basis your invoice states, convert to mass, and never mix a 15 C invoice with an ambient tank dip.
PPAC correction factors, 29.5 C to 15 C
- Petrol: 0.9830
- Diesel: 0.9879
- Kerosene: 0.9864
- ATF: 0.9862
- Light diesel oil: 0.9877
- Furnace oil: 0.9899
Which one applies to you
- Bulk invoices from oil companies usually state volume at 15 C, or print a density at 15 C.
- Retail pump receipts are at ambient temperature.
- Your tank dips are at whatever the tank temperature is that day.
The safe method
Convert every quantity to kilograms with the density for its own basis, then apply a per-kg CO2 factor. A summer reconciliation that compares ambient dips with 15 C invoices can show a 1 to 2% gap that is temperature, not theft.
What Senseible does here
Senseible reads the quantity and unit printed on each fuel invoice, converts it with a stated density or calorific value, and shows the factor and source on every line, so a litre or kilogram is never guessed.
Sources: PPAC Ready Reckoner FY 2025-26, Chapter 9 conversion tables
Last reviewed 2026-10-23.