IN ORDER TO ELIMINATE THE APPLICATION OF TEL WHICH IS TOXIC AND POLLUTANT IN GASOLINE TO INCREASE THE OCTANE NUMBER OF THE GASOLINE, VARIOUS EFFORTS SUCH AS THE ADDITION OF METHANOLAND TERT-BUTYL ALCOHOL (TBA) TO THE GASOLINE CAN BE DONE. THIS STUDY IS FOCUSSED ON WATER TOLERANCE BEHAVIOUR OF THE GASOLINEMETHANOL MIXTURE WITH OR WITHOUT THE ADDITION OF TBA AS COSOLVENT, RE;LATED TO VARIOUS METHANOL-BTA CONTENTS AND TEMPERATURS. WATER TOLERANCE IS IMPORTANT TO KNOW. IT EFFECTS A LOT THE STABILTY OF THE GASOLINE-METHANOL-TBA MIXTURE.