The newer JTD engines have the fuel injection under constant pressure to the engine, this makes them more responsive and powerful. So with the newer JTD engine, a 2.3 is more than adequate for the size of van you are wanting. I have this engine on my Trigano, and it really does perform well. If you are buying a van with the older TD engine, then i would personally go for the 2.8. Also the bigger engines do not use that much more fuel, because the torque is that much higher, you are using lower revs and a higher gear on the hills.