60mpg at 60mph isn't too hard in the mk4 Jetta TDIs either. I avg'd better than 60mpg on a trip from central CA to eastern WA last December... no engine modifications, and only a grill block.
You can see it in my fuel log... when I'm the one driving, I can get pretty high commute mpgs even with stop & go driving.
Further aero mods would help as well...
