This experimental investigation highlights Karanja oil, a nonedible, high-viscosity straight vegetable oil (SVO), blended with fossil diesel (FD) in different volume proportions [Karanja biodiesel 10 (KB10), KB20, KB30, and KB50] in order to assess the oil characteristics and emission analysis on a diesel engine at varying load conditions (0, 2, 4, 6, 8, and 10) kW. Results depict that brake thermal efficiency (BTE) increases, while brake-specific fuel consumption (BSFC) decreases with increase in blend percentage of diesel. Nitric oxide (NO) shows an increasing trend because Karanja oil has high viscosity, low volatility, and low heat content in comparison to FD. Similarly, carbon monoxide (CO), carbon dioxide (CO2), and hydrocarbon (HC) emission were the lowest with that diesel. In general, emission characteristics were discovered useful for KB20 over the entire range of engine operation.