If you have ever compared Diesel fuel and gasoline, you know that they are different. They certainly smell different.
Diesel fuel is heavier and oilier.
Diesel fuel evaporates much more slowly than gasoline - its boiling point is actually higher than the boiling point of water. You will often hear Diesel fuel referred to as Diesel oil because it is so oily. Diesel fuel evaporates more slowly because it is heavier. It takes less refining to create Diesel fuel, which is why it is generally cheaper than gasoline. Diesel fuel has a higher energy density than gasoline.