In fuel testing, a deviation in specific gravity from the expected value could indicate what?

• A. Better lubricity.
• B. Higher flash point.
• C. Lower density only.
• D. Adulteration or wrong grade.

Answer: (D)

Specific gravity compares a fuel’s density to water at a standard temperature, and each grade has an expected SG range. If the measured SG falls outside that range, it indicates the product’s composition isn’t what it’s supposed to be. This is most consistent with adulteration (adding other substances) or using the wrong grade, since those changes directly affect density. Other properties like lubricity or flash point depend on additives and volatility, not just density, so an SG deviation alone isn’t a direct indicator of those traits; and SG can be higher or lower than expected depending on what was mixed. Temperature corrections matter, but after correction a persistent deviation still points to adulteration or wrong grade.