In applications where storage volume is limited, high-pressure storage methods have to be used e.g. compression of natural gas for use as a vehicular fuel, in order to increase the energy storage density at ambient temperature so as to give an adequate driving range. Absorption of methane in solvents can be used to enhance this density. In this paper, the solubility of methane in a total of 46 various solvents has been calculated based on the predictive Soave-Redlich-Kwong equation of state (PSRK model). The results show that among these solvents, neopentane, n-butane, n-pentane, i-pentane, methylethylether and diethylether show the best results. When methane is dissolved in the C5 fraction, the liquid phase at storage possesses a large expandability so it is easy to liberate through a flash separator. The calculation results of this paper show that the storage pressure can be reduced to 15 MPa, and due to the storage condition in the liquid phase, the energy density is increased and a total 20.9 kg fuel mixture including 6.93 kg of methane can be stored by a 501 tank. From this amount 20 kg fuel gas can be liberated through a heated flash separator (compared with 15.3 kg natural gas stored at 25 MPa by the CNG method). Through these investigations, the importance of this study has been illustrated. In Section 4 of this paper, based on the investigation of existing experimental data and the calculated results, an application for measuring P-x-y-rho diagrams of three systems was proposed at the University of Oldenburg. (C) 1997 Elsevier Science B.V.