Since my current truck is for sale, I have it programmed back to stock now. It's showing 13.5 L / 100 Km or ~17 mpg (US gallons) in the driver info thingy - should be reasonably accurate. The 6.4L Hemi 2500 I test drove showed an average of about 17 L / 100 Km (13.8 mpg) in similar mixed driving. The test drive route was about 50/50 city/hwy.
Right now, diesel fuel is $1.47/L here (about $5.55 per US gal), and reg unleaded is $1.27/L ($4.80 per US gal).
So, to drive 100 Km (62 miles) it would cost me roughly:
- Hemi, 17 x 1.27 = $21.50
- Cummins, 13.5 x 1.47 = $19.85
On the dealer lots here, the 6.4L Hemi is a $2000 option, and the Cummins is $9350, plus the 68RFE adds more to the cost over the 66RFE, so it's about an $8k difference in the cost of the truck.