Nanofluids with different energy dissipation capabilities were developed with various inner pore diameter multi-walled carbon nanotubes (MWCNTs) and nonwetting high surface tension liquids. MWCNTs were surface treated by different chain-length organic groups to improve the energy dissipation properties. It is found that with increase of the inner pore diameter of MWCNTs, energy dissipation capabilities of the nanofluids decrease correspondingly. Furthermore, the coverage rate of the grafted organic groups on tube surfaces, controlled by the relationship between MWCNT pore diameter and organic chain length, is found to be the key factor for the nanofluids to achieve maximum energy dissipation capability. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.