In this paper, sensitivity analysis of fuel adulteration has been carried out. Kerosene is used as an adulterant due to its easy miscibility and cheap cost. It is noticed that net refractive index (RI) of adulterated diesel decreases as the kerosene level increased but reverse in the case of adulterated petrol. In our proposed sensor, we utilizes the etched Fiber Bragg Grating (eFBG) which enhanced the interaction between evanescent field and sensing medium to a greater extent. Concentration mixing is chosen in the succession of 10% in each case to detect the adulteration level in kerosene-diesel and kerosene-petrol. The experimental results of Bragg wavelength shifting and sensitivity was investigated. Sensitivity of 26.97 nm/RIU in the case diesel and 49.98 nm/RIU in the case petrol were recorded respectively. This kind of sensor is suitable for real time on-road sensing.