I have a STONE stock '06 3500 SRW 4x4 auto, with 3.73's. Here's what I've found:

PUMP THE FRONT TIRES UP TO 80 PSI. These trucks new are prepped by the dealer to have the pressure called for on the doorjamb sticker. This is insufficient for good mileage-it will cost you at least 1.5 mpg to run only 50 psi in the front tires, and probably more. 80 psi is safe, as it is the max recommended pressure on the tire sidewall. Rear pressure can vary as needed for the load being hauled, but in general is probably best at around 60 to 65 for an unloaded SRW, and probably 50 or 55 on an unloaded dually.

Run it in tow/haul mode all the time-that lets the converter lock at 30 mph in 3rd gear, and mine will lock the converter in overdrive a littler earlier than it will in regular mode. Like you have found, do not go exceedingly light on the accelerator pedal until you get the converter locked. Slightly faster acceleration to 30 mph go on and get it locked up is better for economy then endless light throttle heating up of the converter at 28 mph.

Once locked up, try to keep it there. Look ahead at traffic conditions-are brake lights coming on? Is that traffic light 1/4 mile away red? Let off and coast. The earlier you let off, the less you have to slow down. This means that your chances of staying in the converter lock zone improve. If you do have to slow down to the point that it unlocks, slowing down earlier but less will mean you're that much closer to being able to re-lock the converter when you can speed back up.

Put it in neutral at traffic lights. It's a small thing, but it uses less fuel at idle if it does not have to sit there and slip the converter. OR, shut it off completely at long lights. I do that a lot myself.

Get the "hard start" flash done if your truck is eligible for it. Hard starting is the chief complaint that will get that one done, and it's pretty consistently good for 2 mpg. It's an '06 only flash, and your truck may or may not be eligible depending on what software version it left the factory with. Can't hurt to try.

Last thing-like others have said, those short trips are mileage killers. Try to combine trips if you can.

 

Highway speed less than 70, mix of highway and rural roads (whats a city?) I am right at 20mpg or just slightly over- combined.

BUT I have the G56 manual and I shift in the low teens and go easy on the right foot. Also, I am coming up on 12,000 on the odo and the mileage has improved slightly but steadily.

Your highway mpg's might be slightly better than mine due to your higher gearing, but the lack of slip in my drivetrain combined with being able to shift at lower speeds probably accounts for my better combined.

But any fuel mileage in a CTD feels so much better than a gasser!!

John

 

There's lots of good info and tips here. But for the average person on any given day, the three rules for getting better fuel mileage are:

1. Slow down
2. Slow down
3. Slow down

If its not enough, go back to #1 - or strapping a raw egg to the throttle to prevent you from pressing too hard.

Drive smart, not aggressive.

 

The RokkTech sensor is a factory sensor with some plastic shaved off so you can advance the timing a couple of degrees. I've read comments from Cummins Engineers and they are quite frank that the engine will run better and get higher MPG with a couple of degrees of advance, so unlike other "mods" this one doesn't ask the engine to do anything its designers didn't intend.

A tonneau cover improves the airflow over your truck, which at higher speeds is probably your number one issue affecting MPG. These trucks are NOT aerodynamically efficient, and air drag increases with the square of velocity so it gets MUCH worse as your speed increases. That's why bigger tires often reduce mileage even though they improve the final drive ratio - they degrade the efficiency of the airflow beneath the vehicle (there's a reason race cars are built very close to the ground). There is much dispute over whether the effect of a tonneau cover, or removing the tailgate, is real... but I can tell you from personal experience that with a 2006 Dodge Ram 3500 QC SB the effect is VERY real, to the tune of 1-2 MPG repeatedly, every tankful.

These two things should yield you a solid 3+ MPG increase. They are neither permanent nor irreversible, so you can back out of them if you wish. They are not expensive. You can install them yourself.

With studded snow tires at ~45 PSI, cold weather, and ULSD I'm still getting ~18 MPG, which I consider reasonable for this time of year. In the other three seasons on the stock Michelins I get close to 20 MPG.

Hope this helps!

 

The rokktech sensor is a tossup, ON THE '06s ONLY. I don't know why, but people who put them on earlier-than-'06 trucks seem to always get better mileage. People who put them on 06's seem to be divided about 50/50 as to whether or not they see a gain, with some seeing a slight loss. I don't know how to explain this myself, but I bought one and tried it on my '06. Mileage was the same or SLIGHTLY decreased, so I sold it. I'm not knocking the product at all, just saying that it may or may not help on a 2006 truck. I knew this before I bought it, so there were no surprises to me.

Tire pressure, slowing down, and looking ahead to let off early will make a big difference.