This paper presents the methodology and results of vapour pressure measurements and vapour phase composition determinations of M20, M50, M70 and M85 methanol-gasoline blends. These blends were chosen to span the range of composition which could be found in a variable fuel vehicle tank. Vapour pressures were measured at seven temperatures from -40°C to 40°C and at vapour liquid ratios of 4:1 and 500:1. The vapour phase composition was determined for these two vapour liquid ratios at temperatures of -28.9°C (-20°F) and -17.8°C (0°F). This paper also compares the theoretical predictions of vapour pressure and fuel/air equivalence ratio of the Royal Military College multicomponent fuel volatility model to the experimental measurements.