The PVT properties and bubble point pressures for compositionally characterized commercial grade samples of butane, 2-methylpropane, and natural gasoline have been measured using a continuously weighed pycnometer and a vibrating tube densimeter. The results cover the range of pressures from the bubble point to 9.7 MPa in the temperatures range from 255 K to 322 K. Experimental uncertainties are reported for the temperature, pressure, and density measurements. Measurements conducted at Texas A&M University and at Phillips Petroleum Co. agree within the estimated uncertainities of the two experimental methods.