Despite the notable properties of acetone due to its volatility and oxygen content as a fuel additive, very few studies have been limited to small size special purpose engines. A comparative testing and 3D incylinder combustion CFD studies are presented for acetone-gasoline blend in an i-DSI commercial car engine as the first time. The blends contain mass ratio of acetone by 0-2-5-10-20% (G100-A2-A5-A10-A20). In testing, torque reduced 0.33% (A2), 0.66% (A5), 0.84% (A10), and 1.45% (A20) compared to gasoline. The BSFC decreased by 0.27% (A2), 0.55% (A5), 0.79% (A10), and increased 0.26% (A20). Volumetric efficiency decreased by 3.2-6.4-5.1-11.5% for A2-A5-A10-A20. The CO emission for blends is less than gasoline by 1.5% (A2), 4.0% (A5), 15.2% (A10), and 33.6% (A20). The CO₂ decreased 0.8% (A2), and increased 1.3% (A5), 4.6% (A10), and 11.4% (A20). The HC reduced by 7.0% (A2), 10.1% (A5), 23.8% (A10), and 34.4% (A20). The NO_x formation increased by 3.6% (A2), 4.4% (A5), 27.6% (A10), and 87.8% (A20). Acetone addition decreased torque and slightly increased BSFC. CO and HC decreased while CO₂ and NO_x increased with increasing acetone ratio. Acetone indeed improves the combustion while its final effect on engine performance is not found to be favorable.