Most major regional automotive markets have stringent legislative targets for vehicle greenhouse gas emissions or fuel economy enforced by fiscal penalties. Large improvements in vehicle efficiency on mandated test cycles have already taken place in some markets through the widespread adoption of technologies such as downsizing or dieselisation. There is now increased focus on approaches which give smaller, but significant incremental efficiency benefits, such as reducing parasitic losses due to engine friction.The reduction in tail pipe CO2 emissions through the reduction of engine friction using lubricants has been reported by many authors. However, opportunities also exist to reduce the lubricant viscosity during warm up by the thermal management of the lubricant mass. This presents an attractive proposition to vehicle manufacturers because of the favorable cost-benefit ratios of thermal management systems and because this strategy can achieve some of the benefits that ordinarily require the lubricant viscosity grade to be lowered.In this paper the experimental results from chassis dynamometer tests are analysed. The performance of two modern vehicles was determined using various lubricant thermal management strategies, including removing lubricant from the sump and pre-heating it during the vehicle soak period. The effect of these strategies on the emission of CO2 from the vehicle is described with reductions of up to 1.2% measured on the vehicles tested in this study.