Convert to 15°C if HSD Specific gravity is 0.834
To convert specific gravity to a temperature in Celsius, you need to use a conversion table or formula specific to the substance in question. In this case, the specific gravity of High-Speed Diesel (HSD) is typically used for calculating density and not temperature.
If you are referring to the density of HSD at a specific temperature, you would need additional information such as the temperature-dependent density values for HSD.
If you are looking to convert the specific gravity of HSD to a temperature of 15°C, it is not possible to do that directly without additional information.