Ethylene glycol based nanofluids containing titania nanoparticles up to 8 wt% show the Newtonian behaviour over a shear rate range of 0.5-10(4) s(-1) at 293-333 K. The shear viscosity of the nanofluids (eta) depends strongly on temperature and particle concentration (phi). The normalized shear viscosity with respect to the based liquid viscosity (eta(0)) is found to be independent of temperature and can be given as eta/eta(0) - 1 = 10.6 phi + (10.6 phi)(2). Such theological behaviour is explained by the aggregation mechanism. A combination of the aggregation mechanism with the Maxwell and Bruggeman models gives a good prediction of the effective thermal conductivity of the nanofluids. (C) 2007 Elsevier B.V. All rights reserved.