[slowmover]

Overhead mpg readout is usually off by a percentage. Say, 11%. Mine is high by .75/mpg 55-60/mph. I use it to check effects of external factors on fuel mileage.

Yours being so far off makes me think a tuner has been present. MADs Smarty JR is the best recommendation on that. I'm generally not in favor of them, but this one will allow stock programming to be run among other options. Read up over on CF. I would not allow dealer to reflash.

Injectors (with associated expenses of feed lines) is a good deal more than $1800. $3500-5000 is more like it after everything is tallied. Read all you like about problems with remanufactured injectors. Not good at all. Failure can mean loss of engine. Brand new only. And then only from particular sources. On CF, read posts by Steelhead01, Cerberusiam, PWong and AH64ID (actually, for any and all tech questions). Best step now is extra fuel filtration. Nice kits available. Glacier Diesel and others. See thread by AH64ID. Baldwin brand only in OEM position.

I wouldn't assume injectors are a problem without some evidence. You've so far not mentioned smoking at startup or other warning signs.

No, bad FE can have other sources. The classic ones are wrong tires, lift kit, CAC leaks, alignment, steering, brake caliper drag and fuel or air filtration. And climate plus terrain.

Missoula, MT is cold. And not flat. 13-mpg town is hardly off for a truck a few years along on short trips (under 45-miles). Under 41F you need the MOPAR winter front (and to be plugging in the engine overnight no matter temps). Oil temps come up much more slowly than coolant. And coolant won't get anywhere near 187F this time of year without the WF. Not when you're empty, solo. Oil has to be up near 220F for economy.

IOW, I have yet to see anything to be disappointed about.

I've said use of CC on highway for any condition of load makes consistent test results. So, too, about both shifting and cruising in town. All at 16-1800 rpm. Lower won't produce much change in mpg results. It's easy to do which is important for steering and brake inputs. It's how to teach someone to drive one of these. Steering and braking are higher on the scale in driving one of these without wasting energy. Focus on them. Steady rpm, and when (and how) to brake, to steer, to accelerate. It simply isn't a car. Throw the undisciplined teen out of drivers seat. We all have to at some point.

Choose rpm (gear) and let speed fall where it may. 16-1800 consistently (underlined) makes all else stand out. Use it for now. You've other concerns more important. (And these trucks have no business being in OD below
45).

Have you put it on a scale yet? Put tire pressure to factory spec? The truckstops carry Howes Meaner Cleaner. Throw in a double dose (or higher). Schaeffers Diesel Treat is best everyday, but not so easy to find. The Cummins service house should have their proprietary formula. Check website first. That last is best, and coming downwards in effectiveness with the others. Add to tank first and fuel on top of it (after new filters which you can change yourself per directions. Fuel is Baldwin, and air is MOPAR.

Play in steering is my guess if temp control isn't it. And even new that truck wasn't good (2WD like mine is IFS with rack & pinion). Synergy brand components plus new steering Redhead or MOPAR box and Borgeson shaft are likely necessary. Research using these.

4WD front end / steering ("death wobble") and injectors are the big expenses on pre-2009 trucks. All else but some minor electrical is reliable.

Besides, 100 miles is too short for a test. Do a highway loop of 200 miles as outlined above. Town mpg is a percentage change and (italicized) only if operating temps are already met will that be low!

Hit one of the Pilot truckstops there. Sign up for the RV discount fuel card (see website first). Fill at the big truck pumps. This is practice For When you have your trailer Avoid Car pumps.

Go inside after pulling up and have fuel desk run transaction ahead (cash, or on card; set up more than you'll use and get balance afterwards). Buy the Howes Meaner Cleaner off shelf near fuel desk. Ask them (Scale master) how to use CAT Scale (even though you've read up at their website).

Put additive in tank and fuel. Put handle on lightest feed. May have back out nozzle some. When it pops off, stop. Do not top off as you'll do this on return also. Pull truck forward to line ahead and return to get cash change. If not, enter CAT Scale correct direction (same as entering fuel island, look for sign) and pull up to annunciator. Push button and wait for Scale master. Tell them you are private (they need name, use yours or just "Dodge") and get back into truck. Axles should be on different pads.

Leave and park when told reading done. Go to fuel desk and pay the $11.

Ease onto the Interstate and set cruise at 58/9-mph. Note rpm and use that in future. 100-miles out to a crossover you've already verified via satellite allows minimal turnaround time. No parked idling. Roll on back to same pump and refill the same way.

This is your baseline. Truck tires to 50/55-psi cold (read before leaving house). Axle weights and overall "empty" weight now known. Compare to online towing guide published weight figure.

As to fuel: You want odometer miles recorded and engine hours. With a known travel set speed and rpm, after refill you want to again record engine hours to find average speed.

Average speed matters. (As does average mpg). These numbers will be used
against loaded conditions. And in analyzing hitch setup with trailer. They are vital.

Rest easy. If it seems good it probably is. It's a working vehicle, not a commuter go kart. Differences are in costs. But the owner and operator can keep those minimal.

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