Doing some math here on the fuel consumption stats. Looking at the 2,300 mile trip listed above and my estimates show cost savings on the low side of $100 and up to $235 on the high side.
Personally I average 3,000 miles towing (and 50 nights camping) annually. So at my current pace I'm paying worst case of $300 more per year in fuel than a diesel owner.
I still expect to be tempted by diesel the next time I'm buying a tow vehicle, but I know it won't pay for itself in fuel costs alone.
Best regards,
Chris