The Triacetin [C H14O6 ] additive is used an anti-knocking agent along with the bio-diesel in DI- diesel engine. In the usage of diesel fuel and neat bio-diesel knocking can be detected to some extent. The T-additive usage in the engine suppressed knocking, improved the performance and reduced tail pipe emissions. Comparative study is conducted using petro -diesel, bio-diesel, and with various additive blends of bio-diesel on DI- diesel engine. Coconut oil methyl ester (COME) is used with additive Triacetin (T) at various percentages by volume for all loads (No load, 25%, 50%, 75% and full load). The performance of engine is compared with neat diesel in respect of engine efficiency, exhaust emissions and combustion knock. Of the five Triacetin- biodiesel blends tried, 10% Triacetin combination with biodiesel proved encouraging in all respects of performance of the engine.