A tire pyrolysis liquid (TPL) has been blended in 5vol.% with commercial diesel fuel (5TPL) and tested in a light-duty diesel Euro 4 engine (with all technologies for meeting Euro 5) under transient operation by means of Road Load Simulation (RLS) and simulating the New European Driving Cycle (NEDC). Commercial diesel fuel has also been tested for comparative purposes. In order to characterize engine operation, parameters such as relative fuel/air ratio, exhaust gas recirculation (EGR) valve opening and coolant temperature have been registered. Regulated (THC, NOx, CO) and unregulated gaseous emissions (CH4, C2H4, C3H6 and SO2), smoke opacity and particulate matter (PM) emissions have been monitored for both fuels (5TPL and diesel fuels) during the tests. The EGR valve opening has resulted to be slightly higher for 5TPL than that for diesel fuel. Although the EGR valve opening has some influence on the gaseous emissions, both properties and composition of the 5TPL also showed an important effect. In this regard, these results have demonstrated the potential usage of the TPL for being blended with commercial diesel fuel for light-duty diesel engines without constructive modifications although some properties of TPL should be improved if the blending percent is intended to be increased. Thus, the reduction of sulfur content seems to be one of the major issues to be overcome if both lower THC and PM emissions, and marginal sulfur poisoning of the catalyst are wished.