Given that diesel fuel weighs about 900 grams /litre the fuel weighs 135 kg. To that you add the weight of the tank itself, which will depend on the type of material used and its thickness.
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you're getting too tangled up in the maths here just allow roughly 1 kilo to the litre and it will work out near enough, given that the weight of the container and it's acompanying hardware is not known and that is assuming the tank is exactly 150 litres which I will bet my undies it's not
allow around 140 - 150 kilos for your diesel and 10 - 15 kilos for the tank
take a stab in the dark and say 155 - 160 all up and you wouldnt be too far off!
A 150L steel tank is likely to weigh MUCH more than the 10-20kg estimated above. Standard Troopies have dual 90L tanks from memory... A 150L tank would be aftermarket and I would guess at 40kg....possibly more...
I'm not sure of the weight of an empty diesel tank, I have dropped many in my time and replaced them myself and never really thought that much about it
assuming a few things here but I do a lot of concreting around home and am very familiar with a forty kilo bag of cement, I dont think a troopy diesel tank would weigh as much as that