Nonrenewable fossil fuels are in higher demand, and with fossil fuels rapidly reducing, alternative fuels seem to be in higher demand as well. Blended fossil fuels and biofuels are unlike anything else on the market. Biodiesel was made from Shorea robusta seed oil utilizing a single-stage esterification technique with KOH as a catalyst in the present study. Fuels-based Shorea robusta biodiesel mixtures of SRME20, SRME30, SRME40, and SRME10 were created, and its impact on the experimental results, environmental properties, and energy loss for the VCR engine was evaluated. The flow rate, weight, and percent mixes of fuel with 4 stages were used as process parameters in experiments and it was designed by the Taguchi procedure with the L16 analytical model. Grey evaluation was also used to determine the best mixture of operating conditions to optimize the dynamic response, such as BMEP, BSFC, V, HJW, HJGAS, CO, NOx, and HC emissions. The ideal outputs for the productivity and thermal emissions of the variable compression ratio engine were found to be a compression proportion of 18, a mass of 9 kilograms, and a diesel mix of SRME20, according to experimental inquiry and optimization analysis. However, the comparison investigation found that when using diesel fuel, NOx, HGAS, BSFC, and BTHE emissions increase by 10%, 11%, 15%, and 7%, etc, whereas CO, HJW, and hydrocarbon discharges decrease by 3%, 17%, and 19%. The observed GRG value and the anticipated GRG at an optimum configuration (A3B4C3) are 0.7654 and 0.892, respectively, with a 1.2 error. The experimental results showed that SRME20 might be used as a fossil diesel substitute in the VCR engine. © 2023 Elsevier B.V., All rights reserved.