Jet fuel is 6.4 lb/gallon.
“One gallon of diesel fuel weighs approximately 7.1 pounds.
This is heavier than gasoline, which weighs about 6 pounds per gallon on average.
JetA fuel, a type of kerosene, has a weight of around 6.8 pounds per gallon, making it lighter than diesel but slightly heavier than gasoline.
The weight of these fuels can vary slightly based on temperature and specific composition, but diesel consistently has a higher weight per gallon compared to both gasoline and JetA.”
There is apparently much variability in just how many and which hydrocarbons are in any given gallon of commercially available fuel categories.