The mass of the fuel in the tank can be calculated by multiplying the volume in full tank to the density of the gasoline. First convert 22.3 gallons to ml by multiplying it with 3785.412 since the conversion factor is 1 gallon= 3785.412 ml. Then multiply the volume with the density. Since the density is in g/ml, you would get a value in grams so convert it to kg by dividing it with 1000. The convert the value in kg to lb multiply the value by 2.2. The values are 69.27 kg and 152.72 lb.