millage good, bad or average

[Dodge5256]

i just calculated out my millage i used 46 gallons to go 670 miles. that calculates out to about 14. 5 mpg. my over head computer says im getting 21. 2. i know there not 100% accortate but dam thats off. my truck is stock 06 5. 9 4x4 3500 quad cab dually manual, except for a 5inch exhaust, a smarty, afe stage 2 intake , afe intake horn and a pack brake ebrake. i do 50/50 highway/ city driving. my commute to work is about 12 miles. would this millage be normal or bad. i was hoping to see atlest 18mpg. my 99 with 10 inches of lift on 38 inch mt's with other then the lift and some mach 2. 5 injectores it has the same mods as the 06 but it gets 19mpg hand calculated. almost forgot the 06 has 58k on it and the 99 has 120k. any ideas as to why my 06 gets lower millage. this is embarrassing my buddys 88 k2500 350 gasser gets better millage. he gets 15 hand calculated and he has the same commute. what gives. if i was hotroding the truck around i could understand getting 14. 5 but i drive like a granny, well most of the time.

 

[JVolpe]

Well for 50/50 highway/city driving with a 6sp that may be about right. Not sure how much lower gearing the 6sp is than my 48re.



The Smarty or any performance mod will definitely make the overhead mpg off. They are not accurate completely stock from my experience. Now mine is about 6. 5 mpg high with my mods.



I average around 15. 5 city and 17. 5-18. 0 highway at 75mph. Considering my mods and the Smarty on SW #9 (PoD 55%) I can live with it. If I load SW #5 and drive 70mph I get 19+ on the highway.

 

[Motorhead]

I have an '07, 5. 9, G56 SRW 4x4 and I get 16 in town and as good as 20. 5 highway. Anything over 2,000rpm in 6th, I see the mpg go down. With my AE ratio G56, 2k rpm is 65mph.

 

[Schrowang]

My 04. 5 started out lousy, but as the engine broke in the MPG got better. With 88K on the engine I get 19. 0 50/50, 24. 0 full interstate and 17. 0 around town. That's all hand measured. The overhead is off by about 4mpg (high).



Towing my 5'er I get 13. 5 to 14. 0 depending on the road (highway or local).

 

[SBeretz]

Seems a little low to me. I have the same truck with the earlier G56 and get about 20+MPG's if I stay around 2000RPM's. . Don't know, maybe winter fuel is pulling it down some. My buddies father has an 06 Dually with about the same mods as yours and an automatic and he cannot break 15MPG no matter how he drives. Me and my buddy booth took his truck for a slow ride for about a 100 miles and then hand calculated and it was still in the 14. 5 MPG range. I think some trucks are just thirsty that way. Maybe an injector flaw or something. His truck runs and drives identical to mine, but he just gets lower fuel mileage. Don't know. Scotty

 

[osiris]

where are you from? It is getting colder here so I have been letting my truck warm up for about 15 minutes everyday and my milage have suffered i think i am around 12. 5-13 in town... oh well its really fun to drive!!!

 

[Dodge5256]

i guess im not getting that bad then i drove to my parents today wich is 100 miles and drove a total of 215 miles and burnt 12 gallons so i guess im not doing to badly. would something like a overdrive unit or semi tires help since both will lower my rpm at a given speed. i have 4. 10's to at 65mph im spinning 2100rpm. i guess doing 70mph at 2350rpm and getting 17 on the highway is not that bad. thanks for all the insight.

 

[LRutigliano]

Did you input the correct tire diameter into your ECU with the Smarty? Maybe you are travelling more than you odometer is registering with those 38's...



From my experience, tire pressure has alot to do with mpg's. I keep my E rated tires as high as I can (80 psig) and it makes a difference with fuel economy vs. 65 psig or lower...

 

[Blu-meanie]

Could be the 9,000 lb truck, more horsepower, and the training wheels. That's about what I get when not traveling anywhere. I did a 17. 5 once driving 90% freeway.

 

[AMcCormick]

I'm averaging between 17-19 for mixed driving around the greater SF bay area. Average speeds are around 30-35mph using the engine time and odo readings. If i go on a road trip with higher averages the mpg goes up a bit but not much.