The modern HSDI Diesel engine has demonstrated a tremendous emissions reduction potential over the recent two decades. European legislative limits required a reduction of gaseous and particulate emissions down to and below 1 - 5 % of the 1970 levels. An additional challenge has now been raised by the ACEA/EU-Parliament agreements to reduce CO2 fleet average values (equivalent to fuel consumption) stepwise down to 140 - 120 and finally to 90 g/km in the New European Drive Cycle (NEDC) test.The paper describes the conflicting requirements for both emissions and fuel consumption reduction. Corresponding engine- and vehicle-sided technologies and measures must be considered in order to arrive at the best possible compromise. It is concluded that, taken the imminent CO2 fleet average reduction requirements as serious, a much higher portion of HSDI Diesel powered passenger cars must be sold to the market.