Particulate matter in vehicular exhaust is now under great scrutiny. In the EU, direct injection spark ignition (DISI) engines running on petrol now have limits for particulate emissions set for both mass and number. Current legislative test procedures represent a best-case scenario - more aggressive driving cycles and lower ambient temperatures can increase particulate emissions massively. Ambient temperature is generally the environmental parameter of most importance regarding particulate emissions from an engine, particularly for the reasonably brief periods of operation typical for passenger cars operating from a cold start. Two Euro 5 vehicles with DI SI engines were laboratory tested at three ambient temperatures on two different commercially available fuels, with particulate emissions results compared to results from the same fuels when the vehicles were tested at 25°C. Testing was performed on a chassis dynamometer in a climate-controlled test chamber, using the legislative European test procedure at a total of three test temperatures. The impact of the fuel type of particulate emissions was found to be vastly smaller than the impact of ambient temperature. Particulate emissions increased unambiguously to varying degrees as test temperature fell, sometimes by up to an order of magnitude, when compared to tests at 25°C, confirming the previous findings that temperatures lower than the legislative test temperature lead to increased particulate emissions, in terms of both mass and number. Continuous particle concentration data were used to examine specific periods of the cycle for the impact of ambient temperature.