Automobile fuels — typical density At standard test conditions for road vehicles, the specific gravity (relative density at 15°C with respect to water) of diesel fuel is approximately:

Introduction / Context:
Specific gravity (also called relative density) of automotive fuels is an essential property for engine calibration, fuel metering, and emissions control. For diesel engines, a typical value is expected in a narrow band because the fuel's density influences energy per unit volume, injection characteristics, and atomization.

Given Data / Assumptions:

• Reference temperature for density comparison is 15°C (a common standard in fuel specification).
• Specific gravity is the ratio of diesel density to water density at the same temperature.
• We consider conventional automotive diesel (not biodiesel blends or special winterized extremes).

Concept / Approach:
Typical automotive diesel has density around 820 to 860 kg/m^3 at 15°C. Since water is approximately 1000 kg/m^3 at this temperature, the specific gravity is roughly 0.82 to 0.86. A representative rounded value used for quick engineering estimates is 0.85.

Step-by-Step Solution:
Let rho_diesel ≈ 850 kg/m^3 and rho_water ≈ 1000 kg/m^3.Compute SG = rho_diesel / rho_water.SG ≈ 850 / 1000 = 0.85.Select the closest option to the typical midrange value.

Verification / Alternative check:
Fuel datasheets for automotive diesel list density bands 0.82–0.86 at 15°C, confirming that 0.85 is a reasonable nominal figure for calculations.

Why Other Options Are Wrong:
0.65 and 0.55 are closer to light hydrocarbons or LPG and are far too low for diesel.

0.75 is typical of some kerosenes or light fractions, still low for automotive diesel.

0.95 is near heavy oils and is significantly higher than standard road diesel.

Common Pitfalls:
Confusing specific gravity at different temperatures; density decreases as temperature rises, so use the specified reference temperature. Also, biodiesel blends (e.g., B20) can shift density slightly higher than mineral diesel.

Final Answer:
0.85