This paper describes the results of an experimental investigation conducted to determine the proportion of methanol by volume in methanol-gasoline mixture. The suitability of a Fiber optic Raman spectrometer for in-situ measurement of percentage of methanol by volume in methanol-gasoline is demonstrated. The transformation of Raman spectra of gasoline into Raman spectra of methanol are observed and recorded as the percentage of methanol is progressively increased from 0 to 100%. The measured intensities at the characteristic Raman shift corresponding to gasoline are found to be inversely proportional to the volume of methanol in methanol-gasoline mixture. The results obtained in the form of series of Raman spectra are presented.