This paper intended to indicate the experimental investigation for presenting the influence of employing many fuel additives on spark ignition (SI) engine performance. Three types of fuel additives comprising, Octane booster, Gasoline booster, and Gasoline additive, are added separately with pure Gasoline for a volumetric addition of 2.5, 5, 10 mL/L, 1.5, 3, 6 mL/L, and 2.5, 5, 10 mL/L respectively, whenever 5, 3, 5 mL/L are the normal volumetric addition respectively. An SI internal combustion engine is used with rotational speed range of 1500 - 2500 rpm, wherever the nine blends and the pure Gasoline itself are employed. The results showed improvements in engine performance when using Octane booster. The brake power rises by 8.3%, 14% and 19.4% respectively at the use of half, double, and normal addition of Octane booster compared to that of using pure fuel of Gasoline. Brake thermal efficiency increases to its maximum value by 18.4% when using normal addition, and to its minimum magnitude for using half addition of 7.3% of Octane booster. It exhibited that the magnitude variations in brake specific fuel consumption through using half, double, and normal addition for using Octane booster was 9%, 14.7% and 20.2% respectively compared to employing pure Gasoline only. The results of using Gasoline booster and Gasoline additives found effect on SI internal combustion engine have similar influence as of using Octane Booster. It is noticed that using of additive type Octane booster and using a normal amount of additives lead to reduction in CO concentration in emissions compared with only pure Gasoline and other additives concentrations