I drove down to Melbourne FL from Charleston SC to pick up my bike that had been getting some work done on her for the past month... Weather on Fri and Sat were bad so instead of a rental car and riding bike back....I borrowed a trailer and used the Dodge to recover my lost girl.

On way down I was pulling 1900 RPMs....showing right at 72mph....and with the 295/70/17 Nitto TerraGrapplers I averaged 17.9 on overhead and 18.3 hand computed. 425 miles door to door and around 3/4 of a tank of diesel burned.

On return trip everything was same except had 720lb bike, saddle bags, windshield so maybe another 50lbs...so lets say 750 plus trailer. Ran same speed and rpms....ran air conditioner half way this time instead of entire way like last time (it was raining).....and showed 16.7 on overhead....17.8 hand computed.....same miles for most part....and used slightly more fuel...just below the 1/4 mark but not quite 1/8 of a tank.

The truck has not had the speedo synched as the best you can do is with mopar sized tires they sell...so it is set for 285s like on powerwagon....so guessing that the mileage is pretty **** close and may be slightly better than computed...as I think the larger tires should show worse mileage than indicated as the tire is actually traveling further per rotation than what is loaded in the computer....so I am guessing 19mpg at that speed is accurate. One short stint that was flat I dropped to below 65mph and around 1750 rpms...and it got to 20.2 mpg...but as soon as I got back up to 70 it dropped down. Just glad my overhead is showing worse than hand computed......but not far off so I can use it with some confidence while checking against GPS...which I forgot this trip.

This winter...Volant air kit....SuperChip or Smarty programmer...and a couple gauges...and will see if there is improvement or not on same trip.

 

I make that trip to Charleston from Melbourne about once a year to see a friend or look at a job on one the Coast Guard Ships there.

Your mileage does not sound bad, even with the light tow you had and the speed you were running. My truck has 159k on it and still exibits the same characteristics you just explained when I exceed 70mph. My best cruise speed for mileage is at 68 mph. Once I go over 70 it falls off fast. At 68 running without a tow, its about 19.5.

When I tow anything it falls off. You've got more power than me so it may not be as noticable in your truck. When I pull my Fifth Wheel at 20,500 lbs. combined, I'm at 11mpg for the most part at 64mph. At 55 in Fifth gear its
13.5 to 14.

If you took on fuel in Melbourne, In my opinion, you did not get as good of fuel as you did in Charleston. I usually run from Melbourne to Charleston and then to the last fuel stop in GA to fill up before I go back into Florida. You can tell when you get a good tank and when you don't.

Dave

 

i was wondering about the fuel because in charleston it specified number 2 diesel and gave the low sulfur warning....in melbourne did not specify grade but they wanted 30 cents more than I am paying in charleston...LOL

Next time up here let me know and next time I go to Blackhawk Motorworks I will let you know...we can grab a beer or something.

 

I have the same tires and had the computer recalibrated for the 285's like you said. When compared to my GPS, the speedo is slow by only about .5 mph. Just a little FYI.