Per metric tonne, there are roughly 358 U.S. gallons. The Iowa State University website has conversion charts that show that 1 US gallon is equivalent to 0.002791 metric tonnes. On the other hand, there are 358.294518 U.S. gallons per metric tonne, or 1/0.002791 gallons per metric tonne.
The imperial equivalent of one U.S. gallon is.8321. Add 0.8321 to the number of US gallons per metric tonne to get the equivalent number of imperial gallons. The result of multiplying 358.294518 by 0.8321 is that a metric tonne contains 298.136868 imperial gallons.
Since liquids expand at higher temperatures and contract at lower temperatures, the measurement directly depends on the temperature at which the liquid is measured.