Mass of Substance = Volume of Substance x Density of Substance
Density of crude oil, 48° api = 790.0 kg/m3
Density of crude oil, 48° api in gram/gallon(US) = 23.36309298487349
Mass of a Substance = 23.36309298487349 x 1
1 gallon(US) of crude oil, 48° api weighs 23.36309298487349 gram