Here's all that Mazda is saying about the Mazda3 for now:
"The new 2.0-litre Mazda3 diesel model will be unveiled for the first time. Topping the best???selling Mazda3 model range, the Mazda3 2.0 MZR-CD is fitted with a powerful and frugal engine that delivers 360 Nm of torque – one of the segment's highest outputs – and 143ps (105kW) of power."
I'm inclined to trust that word "frugal." The 2006 Mazda3 made Forbes' list of Top Ten least polluting vehicles last summer. Just a few more days until we can judge for ourselves.