This paper investigates the effect of a small amount of a strong electron-donating solvent (or high electron donor number solvent) on the solvent swelling of covalently and non-covalently cross-linked Kuker-site oil shale kerogen in non-polar solvents. The non-polar (or non-specifically interacting) solvents used in the study were benzene, o-xylene and tetralin. The specifically interacting (or swelling promoting), high donor number solvent added was N-methyl-2-pyrrolidinone (NMP). The changes in solvent uptake of the samples caused by the specifically interacting solvent, previously in equilibrium with respect to a non-specifically interacting solvent, were studied using a Differential Scanning Calorimeter (DSC). The specifically interacting solvent was added in small amounts, up to roughly 2 mmol of NMP per gram of kerogen (that is, 0.208, 0.416, 0.624, 0.831, 1.039 and 2.07 mmol of NMP per gram of kerogen). The experiments indicated an increase up to about two times in the swelling ratio by adding a strong electron donor solvent at 0.8 mmol per gram of kerogen. The effect was most pronounced in the case of tetralin, the solvent with the lowest initial swelling ratio and the largest molar volume. From solvent melting point depression and gas chromatography (GC) experiments, it could be stated that up to 0.8 mmol(NMP)/g(kerogen) most of the high electron donor solvent was absorbed by the Kukersite kerogen. The value 0.8 mmol NMP per gram of kerogen is specific to Kukersite oil shale kerogen. The DSC-based method applied can be considered quantitative up to this limiting value of 0.8 mmol NMP per gram of kerogen, and above this value the results indicate characteristic trends. (C) 2015 Elsevier Ltd. All rights reserved.