NOVELTY - As bio-additive to petroleum diesel, a degummed and transesterified oil obtained from seeds of Olax scandens is used.    USE - As bio-additive to petroleum diesel for enhancing the performance of diesel engines (claimed); in construction industry such as paints, emulsifiers, in pharmaceuticals, cosmetics.    ADVANTAGE - The bio-additive reduces fuel consumption, improves diesel engine efficacy and reduces pollution level as compared to neat petroleum diesel. The bio-additive shows enhanced performance and hence significant engine efficiency at different given loads. The process is cost effective, industrially viable; and the bio-additive obtained has high efficiency, and better biodegradability. The extraction of Olax scandens oil provides economic benefits along with favorable emission and pollution parameters. The Olax scandens oil is highly economic, eco-friendly and an efficient bio-additive which is economically accessible without any seasonal restriction. By undertaking cultivation on large scale, the availability can be assured with short gestation period and all-round the year. The process reduces the free fatty acid profiles, viscosity and improves physical and chemical properties of the crude olax oil. The laboratory process can be scaled up to industrial requirements by conventional methods of extraction, modification and in-process characterizing in commercial scale. The degummed and transesterified oil increases the efficiency of diesel engine. Favorable trend in the fuel consumption pattern of the current bio-additive along with a drastic reduction in smoke, particulate matters and obnoxious polluting and carcinogenic gas emissions, highlights the salient features of the process.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of degummed and transesterified oil obtained from the seeds of Olax scandens involving i) boiling the seeds of Olax scandens in a aliphatic solvent for 4 hours and extracting the crude oil of Olax scandens; ii) adding 1-7C alcohol to the crude oil obtained in step (i) (oil to alcohol ratio is 2:1 vol./vol.), centrifuging, and heating to obtain degummed olax oil; iii) esterifying the degummed olax oil of step (ii) with a lower alcohol in presence of a mineral acid (oil:alcohol:mineral acid of 50:1:0.1 vol./vol./vol.), neutralized with alcoholic base and drying the esterified oil; followed by transesterification with lower alcohol in presence of a base as a catalyst to obtain bio-additive, and iv) separating the bio-additive so obtained from unreacted oil by partitioning with water, followed by centrifuging and recovering.