325/600 fuel economy?

[JPalese]

JPalese,

Here are the secrets and suggestions that I have:

1) accelerate like a grandma to get ON the freeway

That would be me unless safety dictates otherwise... ... ... ... ... ... ... ... ...



2) make sure that you set the cruise and have open road

Yup!



3) resist the urge to "blow by" those rice rockets with full turbo whine authority

No problem here



>>How many miles do you have on the truck?

7800



>>Any hard driving or towing? I noticed a HUGE difference in mine after working it REAL hard a few times (get the cylinder temps up nicely - helps seat rings/etc. )



No, not really. A little bit with a 5500lb boat, but thats nothing for this truck.



Define hard driving... what do I need to do?



>>If you are STILL getting bad mileage, start checking things...

1) Air filter - not restricted?

Looks clear, gauge indicates its in A-1 shape.



2) Change fuel filters



Will try this

3) Change where you buy your fuel - I have noticed up to a 1-2 mpg difference between stations



No difference noted. BTW, with my VW diesel it gets another 3mpg with Amoco Premier, but the truck doesn't change.



4) Make sure you are "filling up" consistently (same amount/cutoff point each time) AND at the same pump for good comparisons



Doing it now. [wife & kids think I'm looney] All mileage hand calc'd.



5) AIR UP the tires . . . esp. if you have stockers - put 'em at 70-80psi

(I was running my BFGs at max pressure)



Will try that mine are 60 psi all around per dealer suggestion.



>>The other thing I can think of is that with stock tires, you are turning more RPMs than I, so you may plummet your mileage above 65, whereas mine does not drop off until 70-72 due to the simple reduction in gear ratio caused by the 34. 6" tall BFGs versus your 31. X stock tires.



With the stock tires in overdrive 1950 RPM = 70 mph. There is a slight decrease in mileage from 1700 - 1950 RPM. Above 1950 the mileage drops off a good bit.



I always thought that since larger diameter tires put the truck higher off the ground they dramatically increased the wind resistance due to the higher profile causing decreased mileage.



>>Best of luck... if you want to PM me your #, we can talk more and compare further via phone...



I may do that, but for now thought an exchange of ideas here might help all the other guys who have the 600 mileage blues.



regards,

John

 

[jcarey]

Totally stock, we have gotten 20. 03 (our personal best). Now with the AFE and the tonneau, I suspected that MPG would rise a bit, but did not. What I have found out is that I'm having more fun Oo. and thus the drop to 17. 08 MPG with yesterday's fill-up. Haven't gotten anything lower than that since the first fill-up, which was in the 16's. Drining moderately, though, we've been in the 18+ and some 19's for most fill-ups. I really wonder if there is such a difference between engines (I now there's some) or more so between driving styles. What I mean is most 4-cyls beat me off the line from the stop light - driving style.



Jim

 

[GEM]

My traded 2000 F250SD Super Cab/ 7. 3L stock Automatic 373LS RE averaged 15MPG/11mpg towing. My 2004. 5 2500 QC 48RE 600HO CTD w/ 373 LS RE seems to be getting around 12/9 towing. So far-2200 miles. What Mods are considered just mileage enhancers. Other than this mileage issue, This dodge is a very nice pickup- so far.

 

[favord]

Nobody wants to admit some of the beloved Cummins might not be working appropriately. I don't discount that driving style could account for some difference in fuel economy but c'mon, I get at best 12-13 empty driving like a grandma and others are reporting 20mpg racing ricers. Something is not right with some of these engines... nothing to be ashamed of or hide from public view. It happens. Just would be nice if something could be figured out to help us out instead of being told to coast, fill my tank up to the top, only drive on full moons, or put my hat on backwards.

 

[SMorton]

My 04. 5 Q/C 4x4 2500 SRW AUTO 4:10 consistently gets 16. 1-17. 3 all around empty, and towing an open car trailer with full size car for 400 miles at average of 70MPH got 15. 3. I imagine if I really drove old lady like it would be better, but I think this is fantastic! Great power and decent economy too!

Mileage currently is 10K, I figure every tank by hand, fuel consistently at the same place near home.



04. 5 2500 Q/C SRW SB 4X4 AUTO, 4:10 Rhino liner, mopar mud gaurds.

Stock so far, but not for long! Special ordered and very worth the wait!!



02 KTM 520 EX/C

 

[thames1948]

Nobody wants to admit some of the beloved Cummins might not be working appropriately. I don't discount that driving style could account for some difference in fuel economy but c'mon, I get at best 12-13 empty driving like a grandma and others are reporting 20mpg racing ricers. Something is not right with some of these engines... nothing to be ashamed of or hide from public view. It happens. Just would be nice if something could be figured out to help us out instead of being told to coast, fill my tank up to the top, only drive on full moons, or put my hat on backwards.

Well said, I will second that for sure.

 

[amsoilman]

It seems the RPM's is where the difference lies on these engines. If kept in the 1500-2000 RPM's they get the best mileage. I know on my 03' HO that produces the best mileage.



Wayne

 

[RCovert]

I have a 04. 5 3500 4x4 QC, SLT, 325/600, 3. 73 with 48RE. When truck had 700 miles on it I got 13. 5 towing 9500+ and 17 on the highway a 68MPR (1850RPMs) empty. The turbo went out at 4000 miles – after they replaced it I started getting 9. 4 towing and 13. 5 to 15. 5 on the highway @ 68MPH empty. I’ve had the truck in twice and they did two “controlled tests” and they got 11. 8 and 14. 8. They can’t find any air leaks or anything else that would cause the drop in fuel mileage.



I now have 6500+ miles now and two weeks ago I thought the truck had solved the problem by its self. Started up the road with a full tank of fuel running a 68MPR (1850RPMs). After 114 miles the overhead was reading 17MPG. I pulled off at the Flying J and topped off and got a coffee - hand calculated 17. 3MPG. Pulled back on the road set C/C a 1850 (68MPR), 150 miles later the overhead was reading 13. 7MPG (hand calculated 14MPG). I’ve been monitoring this and I’ve continued to notice that I get better fuel mileage when I get in and the engine/turbo are cold. When I shut it off after they have warmed up to operating temp and restart while its warm, the fuel mileage drops 3 to 4 mpg town/highway.



Does anyone have any Ideas?

 

[DGStrate]

1) accelerate like a grandma to get ON the freeway

That would be me unless safety dictates otherwise... ... ... ... ... ... ... ... ...



2) make sure that you set the cruise and have open road

Yup!



3) resist the urge to "blow by" those rice rockets with full turbo whine authority

No problem here



>>How many miles do you have on the truck?

7800



>>Any hard driving or towing? I noticed a HUGE difference in mine after working it REAL hard a few times (get the cylinder temps up nicely - helps seat rings/etc. )



No, not really. A little bit with a 5500lb boat, but thats nothing for this truck.



Define hard driving... what do I need to do?



>>If you are STILL getting bad mileage, start checking things...

1) Air filter - not restricted?

Looks clear, gauge indicates its in A-1 shape.



2) Change fuel filters



Will try this

3) Change where you buy your fuel - I have noticed up to a 1-2 mpg difference between stations



No difference noted. BTW, with my VW diesel it gets another 3mpg with Amoco Premier, but the truck doesn't change.



4) Make sure you are "filling up" consistently (same amount/cutoff point each time) AND at the same pump for good comparisons



Doing it now. [wife & kids think I'm looney] All mileage hand calc'd.



5) AIR UP the tires . . . esp. if you have stockers - put 'em at 70-80psi

(I was running my BFGs at max pressure)



Will try that mine are 60 psi all around per dealer suggestion.



>>The other thing I can think of is that with stock tires, you are turning more RPMs than I, so you may plummet your mileage above 65, whereas mine does not drop off until 70-72 due to the simple reduction in gear ratio caused by the 34. 6" tall BFGs versus your 31. X stock tires.



With the stock tires in overdrive 1950 RPM = 70 mph. There is a slight decrease in mileage from 1700 - 1950 RPM. Above 1950 the mileage drops off a good bit.



I always thought that since larger diameter tires put the truck higher off the ground they dramatically increased the wind resistance due to the higher profile causing decreased mileage.



>>Best of luck... if you want to PM me your #, we can talk more and compare further via phone...



I may do that, but for now thought an exchange of ideas here might help all the other guys who have the 600 mileage blues.



regards,

John

John,



Ok, separating out the responses for clarity... Thanks for the replies!



Hard Driving: I was only getting in the 15 range but was running late for a wedding that was in northern MI. Got stuck in the infamous I-75 north construction and was forced to run even later! So, I come out of the construction and "kept up with traffic" - did not even WORRY or THINK about mileage. We were moving at 85-95mph (I know - no flames please! :-( ) so my RPMs were rather high, even with the 3. 73 gears. I was turning 2500-2600 rpms for an extended period in 4th (48RE) gear. Plus, when I would have to "catch up" I would run the truck through 3rd (passing gear). The engine was definitely "working. " Temps were ok (esp since truck is STOCK, plus was empty). I noticed that the next day, on the return trip, I started being able to (when driving 'nicely') get really decent economy & mpgs. As I stated before, I DID repeat my 20+ mpgs several times in the next week on other trips I had to make. I have also, since then, been able to dip back down to 14-16mpgs if I drive having more fun and mix in some city miles.



Air Cleaner Gauge: Just my $. 02 worth - the gauge is useless from my experience, but if you checked the filter visually, cool!



Tires - 60 psi will definitely give a better ride, 80 might help mpgs! My BFGs have some extra "cush" built in from only being a "D" range tire (softer sidewalls).



Also, tires difference... I completely understand what you are saying about the height, but a 3+ inch increase only raises me (without a lift kit of course) 1. 5" extra from the ground, so not that bad. I do notice though that my RPMs at speed are lower than yours (1750 or so at 70-71mph). This may ad to the difference, esp. if you are noticing that above 1950 you get a drop off in mpgs.



I DO feel that there is some discrepancy in the motors and that DC needs to find/fix it. I myself have started having the 64-70mph vibration problem, so I will be attacking that next. There have been some really good troubleshooting tips from fellow members here that I will start with.



Keep us updated with the mileage progress!

Try some hard driving! It sure helped me!



-Derek