The non-edible oil jatropha biodiesel is a diesel blend fuel source for the compression ignition (CI) diesel engines. Hence, the determination of the exact blending ratio of biodiesel to diesel fuel for best engine operation is needed through research. Keeping this in mind, this work investigated various acceptable jatropha biodiesel-diesel blends for diesel engines through fuel properties analysis. In this study, six different volumetric percentages of the biodiesel-diesel fuel samples were prepared. The percentage of the biodiesel was varied from 5 to 30% with a step of 5% by volume. The important properties required for engine operation like cloud and pour point, flash and fire point, density, viscosity and calorific value were measured under standard conditions. The average measured properties of biodiesel-diesel blends were compared with diesel fuel. The possibility of using 100% biodiesel in diesel engines without any modifications is also checked by comparing its properties with diesel fuel. The investigation revealed that the cold flow properties of diesel fuel such as cloud and pour point were improved with jatropha biodiesel blended fuels. Also, the results confirmed the good ignition quality and stability, energy content and atomization property of jatropha biodiesel blended fuels. The diesel and 20% jatropha biodiesel blending (B20) fuels showed an identical pour point temperature of − 3.5 °C. Similarly, B20 fuel has produced only 2.28% lower calorific value and 1.2% higher density as compared to diesel fuel. The other B20 fuel properties such as fire point, viscosity, flash point and cloud point were found within 7.44% to 12.5% higher than the diesel fuel. Hence, the study has recommended the B20 as the optimum blend fuel for CI diesel engines. © 2020, Springer Nature Switzerland AG.