3,5-Dimethyloctane is primarily used as a reference compound in the study of hydrocarbon combustion and fuel performance. It serves as a model substance in research to understand the behavior of branched alkanes in internal combustion engines, particularly in assessing ignition properties, fuel efficiency, and emissions. Its structure helps simulate the characteristics of more complex fuel mixtures, aiding in the development of cleaner and more efficient fuels. Additionally, it is utilized in laboratory settings for calibration and testing of analytical instruments, such as gas chromatographs, to ensure accurate detection and quantification of hydrocarbon compounds.