depends on their use

Gasoline, diesel fuel and fuel oil are all petroleum products.On distillation, Gasoline is formed from shorter and lighter chains of hydrocarbons than either diesel or fuel oil.Gasoline is lightweight, extremely volatile and evaporates quickly. These qualities contribute to gasoline powered engines having more horsepower and acceleration than an equivalent diesel engine. However, gasoline is not as efficient a fuel as diesel or fuel oil. Gasoline produces approximately 124,000 British Thermal Units (BTUs) of energy per gallon (3.79 liters) while a diesel engine produces approximately 139,000 BTUs of energy per gallon (3.79 liters).
Diesel is a middle weight product that is heavier than gasoline. It has the appearance of oil and is often referred to as diesel oil. It does not evaporate as quickly nor is it as volatile as gasoline. It takes less refining from crude oil to make diesel fuel, which often makes diesel less expensive than gasoline. The increased mileage and lower cost make diesel a popular choice of fuel in many parts of the world.
Fuel oil used for the heating of homes is slightly heavier than diesel fuel but shares similar properties and is considered a middle distillate as diesel is. Fuel oil for residential use produces approximately the same amount of BTUs as diesel and has a low volatility which makes it ideal for residential heating. Fuel oil that is used in large industrial applications such as electric power generators are considered residual fuel oils and are heavier than gasoline, diesel fuel, and home heating oil.

Gasoline, diesel fuel and fuel oil are all petroleum products.On distillation, Gasoline is formed from shorter and lighter chains of hydrocarbons than either diesel or fuel oil.Gasoline is lightweight, extremely volatile and evaporates quickly. These qualities contribute to gasoline powered engines having more horsepower and acceleration than an equivalent diesel engine. However, gasoline is not as efficient a fuel as diesel or fuel oil. Gasoline produces approximately 124,000 British Thermal Units (BTUs) of energy per gallon (3.79 liters) while a diesel engine produces approximately 139,000 BTUs of energy per gallon (3.79 liters).
Diesel is a middle weight product that is heavier than gasoline. It has the appearance of oil and is often referred to as diesel oil. It does not evaporate as quickly nor is it as volatile as gasoline. It takes less refining from crude oil to make diesel fuel, which often makes diesel less expensive than gasoline. The increased mileage and lower cost make diesel a popular choice of fuel in many parts of the world.
Fuel oil used for the heating of homes is slightly heavier than diesel fuel but shares similar properties and is considered a middle distillate as diesel is. Fuel oil for residential use produces approximately the same amount of BTUs as diesel and has a low volatility which makes it ideal for residential heating. Fuel oil that is used in large industrial applications such as electric power generators are considered residual fuel oils and are heavier than gasoline, diesel fuel, and home heating oil.