This thesis is concerned with the principal features of solvent resistant nanofiltration (SRNF), and in particular its potential in fuel processing. In the recent and more established literature, dense polydimethylsiloxane (PDMS) has been identified as a potential SRNF membrane with separation properties at a molecular level. This thesis investigates the transport and separation mechanisms of dense PDMS membranes in SRNF applications relating to the filtration of organic solvents (mixtures are mixed to simulate fuel). Simulated fuels were created which comprised representative organic solvents with organometallic (OM) and poly-nuclear aromatic (PNA) solutes. The solvent flux and solute rejection behaviour of the solvent-solute systems were studied using a cross-flow air-driven filtration apparatus and a range of operating regimes.