VAPEX, warm VAPEX and hybrid VAPEX rely on a combination of mass and heat transfer to reduce the heavy oil's viscosity sufficiently for it to flow via gravity drainage to the production well. In the last couple of years, many combinations of vapour extraction and steam-assisted gravity drainage have been proposed for the in situ recovery of heavy oil and bitumen. The question still remains; which technique (VAPEX, warm VAPEX, hybrid VAPEX and/or SAGD) produces more oil with better sweep efficiencies? This paper attempts to define and compare the various enhanced heavy oil recovery techniques, including different solvent choices. The pore-scale mechanisms are identified, key advantages and disadvantages given and the results from simple laboratory experiments are compared to better direct the investigation into the in situ recovery of heavy oil and bitumen. The solvents and solvent mixtures (in combination with non-condensable gases and/or steam) are analyzed based on their physical properties at laboratory and reservoir conditions and the role they play at the pore-scale.