Here I'm tallied the fuelly averages of 2009+ Jettas, 2004-2006 Jettas, 1998-2003 Jettas, and 2012 Passats.
Average L/100 km, weighted on distance driven, fuelly US MPGs for higher precision.
2009+: 6.198
2004-2008: 5.737
1998-2003: 5.440
2012 Passat: 5.837
Fuel consumption difference (compared to 1998-2003 Jetta):
2009+: +13.93%
2004-2008: +5.46%
1998-2003: +0.00%
2012 Passat: +7.28%
Fuel consumption difference (compared to CR Jettas)
2009+: +0.00%
2004-2008: -7.44%
1998-2003: -12.23%
2012 Passat: -5.84%