The relationship between caloric values and SG of fuels

• A. Higher SG's result in higher caloric value per unit of volume
• B. Higher SG's reduce caloric value per unit volume
• C. SG has no relation to caloric value
• D. Caloric value depends only on temperature

Answer: (A)

Calorific value per volume depends on two things happening together: how much energy is released per unit of fuel (calorific value per mass) and how much fuel you can fit into a given volume (the fuel’s density, reflected by SG). Energy per volume equals energy per mass times mass per volume, so as SG increases (density rises), you can pack more mass into the same volume, boosting the energy you get per liter or per cubic meter—assuming the energy per mass doesn’t drop dramatically.

In practical terms, fuels that are denser tend to deliver more energy per unit volume. For example, denser fuels like diesel carry more energy per liter than less dense fuels like gasoline, even if their energy per kilogram is similar or only slightly different. That’s why the statement that higher SG leads to higher caloric value per unit volume is the best answer.

If you compare fuels with very different energy densities by mass, the relationship can vary, but the general rule remains: higher density usually means more energy per unit volume.