How much does a gallon of jet fuel weigh?
Jet A and Jet A1 are the most commonly used Jet fuels; their weight is 6.8 pounds per (US) gallon.
JP-4 is a mixture of wide cut gasoline, kerosene, and oil, it has no anti-ice additives; its weight is 6.4 pounds per (US) gallon.
The smell between the two is entirely different.
ALL JP fuel (4,5,8) has anti ice additives (AKA FSII) if not at altitudes condensation would form and would freeze thus freezing gauges pilots need to fly the plane.