I got curious about general MPGs as experienced (and documented at Fuelly) by owners of the Soul and Forte.
As I checked, I also looked at the Rio and Optima MPGs, as well as the new Elantra and older Spectras and Elantras.
I went to the well, in this case Wikipedia, and educated myself regarding some of the H/K engines.
You can see where Soul got an apparent MPG bump in 2012 when the Nu engine came into the lineup.
Please forgive if this doesn't all go together cleanly, I cut and pasted some of it.
I checked Fuelly for general histories regarding MPG. Here is what I found:
The only 2013* cars listed are the Forte and the Elantra. Other columns start at 2012, except Spectra which starts at 2009 and goes back to 2007.
"Dual-CVVT" refers to Continuous Variable Valve Timing for both intake and exhaust. Otherwise, it's intake only.
2013 2012 2011 2010 2009 2008 2007 /Engine Family
*Elantra 31.0 30.0 30.7 30.0 27.9 28.7 29.8 /Nu 1797cc Dual-CVVT 2013-2011; Beta II 2010-2007
*Forte 25.1 25.3 27.9 /Theta 1998cc & 2359cc, CVVT Intake only
Soul 29.0 26.5 26.5 /Nu 1999cc Dual-CVVT 2012 only; or Gamma GDI 1591cc, Dual-CVVT 2012-2010; Beta II 1975cc 2011-2010
Spectra 29.1 26.7 30.9 /Beta II 1975cc CVVT Intake only
Rio 34.1 30.3 29.3 30.1 /Gamma 1591cc GDI, Dual CVVT, 2012 only
Optima 26.5 25.5 28.6 26.0 /Theta 2359cc or 1998cc (t), with GDI, CVVT intake only, 2012-2011
Spacing didn't work here, could not make clean columns.
Surprisingly, the older Spectras and Elantras with the Beta II 1975cc engine were quite competitive.
Interestingly, the Optima 2.4 GDI (Theta) shows equivalent MPGs to the Forte (Theta) 2.0 and 2.4 which do not have GDI.