need help with my diesel

[panamajr]

ok
i have a 2012 ram 3500 6.7 cummings no lift just a leveling kit and 35" tires
now on a regular day i get 14l/100km but this last trip out to manitoba my truck was getting 40L/100km pulling a 27ft camper trailer about 8000lbs WTF??? they said that it could have been biodiesel that i may mistakenly got but thats BS i know i newver used that there is no chip and have never had one
now my question is why would it get that horrible gas milage around 5MPG
any help would be nice the shop is in AWE

[JB_AOL]

Well for one we need more details.. How fast were you travelling? Any wind? Head wind? Also, which direction were you travelling?

Speed and wind kill mileage.. You're getting about 1/2 of what you should.. Ie, most diesels are getting around 10-12mpg towing.

Are you sure that's what your trailer weighs? were the tanks full (grey/black/fresh)?

Sounds to me like you got a bad tank of diesel, mixed with a head wind.

[panamajr]

i was going east to winnipeg then west back to calgary
tanks in the trailer all empty and was going 120kmph
there was minor wind say 10km wind coming from say 8 or 9 oclock spot

[sco22]

I get about 19-20l/100 km pulling an 8,000 pound 5th wheel with my 2008 GMC Sierra Diesel. But I rarely get going faster than 105. Cannot see why you would get mileage that poor. Sure some of it will be the speed, but there has to be more than that. Where did you buy diesel from?

Cheers.

[JB_AOL]

And I forgot to ask is this Hand calculated? or using the truck's DIC?

All DIC's are notorious for being inaccurate..

If it makes you feel any better.. I get 8mpg towing my 7000# trailer with my gasser..on a good day, down hill, averaging the speed limit..

lol..

[panamajr]

i was getting the fuel from shell and petro canada mostly once from husky along the trip
the dealership is at a loss they have no idea why it was doing this
its bran new with only 20000km on it i had an oil change done t 18000 and they said the oil was black already there has to be something going on . but they cant seem to figure it out

[recce43]

bad injector //// fuel leak are you putting out black smoke ?

[Bennettcw]

All in your speed, I have the same truck, same issue, if I run 100-105 then m arond 19 with no wind 25 with. If I get going anything over 110 it's up to 28/29 no wind to 40 with wind. I dive back and fourth to ontario 4 or 5 times a year and find the best fuel mileage I get is after dark when it's cooler traveling roughly 105

Bennett

[Redfrog]

operator error

[panamajr]

the RPM is only at 1600 at 120km
and there was no smoke and the tailpipe is clean
can going 120 at 1600RPM vers 1400 at 105ish make that big of an average difference??

[JB_AOL]

Actually speed towing does make a large difference but not as large as you are getting.

If I tow @ 95km/hr I get 10mpg, but I get enough glares travelling the speed limit.

You might want to search cumminsforum.com for your issue..

[sourdough doug]

Originally Posted by panamajr

the RPM is only at 1600 at 120km
and there was no smoke and the tailpipe is clean
can going 120 at 1600RPM vers 1400 at 105ish make that big of an average difference??

Axle ratio, pretty long legged IMO, but then again, it's a Fargo
Just noted....maybe you need bigger tires

[leeaspell]

Ditch the 35's and go back to the 265/70r17 and watch the mileage come back. 35's look good, destroy towing mpg, or switch the gearing in rear end to compensate for the bigger tires.


And, are you factoring in the Speedo difference from the bigger tires, which showing 120, your actually at about 132

[full_throttle]

Maybe your computer calibration is out. Did they properly calibrate the tires when you changed to 35" tires ? Thats my guess. I had my computer go out once and revert back to the stock settings.

[AbAngler]

Check your brake controller. Has happened to me.

[panamajr]

Originally Posted by AbAngler

Check your brake controller. Has happened to me.

what about the brake controller?
i tested it but was wondering if i had drag but the trailer brakes never warmed up

[panamajr]

and the truck was set for the bigger tires
i didnt think the tires and doing 12o would put the truck agt 40l/100km
at most i was figureing 22l/100km

[sourdough doug]

Originally Posted by panamajr

i didnt think

....

[Fry]

Like everyone said, have to hand calculate and have to have accurate speedo.
I have a duramax on 37s, speedo accurate, adjusted with EFI live, towing at 120kph and get 10mpg, hand calculated, mostly flat towing.

[panamajr]

did the math and still 36l/100km

[dale7637]

Originally Posted by panamajr

the RPM is only at 1600 at 120km
and there was no smoke and the tailpipe is clean
can going 120 at 1600RPM vers 1400 at 105ish make that big of an average difference??

It has less to do with RPMS than it does engine load.
The front of a camper is a wind sail. The amount of wind a camper has to cut through is amazing. Add in a headwind and excessive speeds and you have the solution to your issue.

The oil is black because you worked that engines nuts off at that speed.
That ought to attract the cummins lovers.

Did the emissions system regen regularly?

Was this hand calculated or did you trust the computer.

[70chevy]

I think I was talking to u at the flying j in Winnipeg,07 blue megacab dodge I was driving.You had a red canoe on top of your trailer?

[coolpete1]

the truck was set for bigger tires but the biggest you can set it for is 285 70 17 , so your milage display and speedo are still out.

[rhuntley12]

2012 3500 dualie, towed trailer down past couer d alene. Went speedlimit whole way. trailer should be about 9000 pounds. Computer said trip averaged 21.3L/100KM. (about 1/3 of the driving was around the city with no trailer)

[cnjb223]

Have you checked the air pressure in your tires?

[gmcmax05]

Originally Posted by dale7637

It has less to do with RPMS than it does engine load.
The front of a camper is a wind sail. The amount of wind a camper has to cut through is amazing. Add in a headwind and excessive speeds and you have the solution to your issue.

The oil is black because you worked that engines nuts off at that speed.
That ought to attract the cummins lovers.

Did the emissions system regen regularly?

Was this hand calculated or did you trust the computer.

The oil is black because he didn't change it for 18,000 kms, I'm not a cummins fan but I doubt it was "getting it's nuts run off " pulling 8000 lbs at 120 km/hr. I drag 13,000 around with my dmax at 110+ and it hardly breaks a sweat.

[leeaspell]

The oil is black because it's doing what it's supposed to do lol

[Duramaximos]

Originally Posted by panamajr

the RPM is only at 1600 at 120km
and there was no smoke and the tailpipe is clean
can going 120 at 1600RPM vers 1400 at 105ish make that big of an average difference??

Wind force increases exponentially with speed. So, yes, you will notice a significant difference in economy with as little as 10km difference in speed.

My Dmax efficiency is 17 mpg towing at 95, 14 mpg towing at 105, and 10mpg towing at 115. In all cases towing 9000# on the same round trip.

[big zeke]

I have the same driveline in a 2011, pulling a 9000# fifth wheel at 105 gives about 18l/100 kms (15ish MPG by my hand calc, based on Imperial gal). It matches up well against my hand calcs every time I fill. When empty that truck has gotten as good as 11.5/100 (24 MPG) and the DIC matches the hand calcs very closely.

I am amazed abt your 40l/100...I'd suggest ditching the 35s and driving at the speed limit (or a bit below if you are willing). If the engine is running smoothly with no codes showing you might be stuck with a gas hog. I doubt you had a dragging brake as you'd have bigger problems than bad fuel economy over that distance.

[ishootbambi]

my diesel got 30l/100 km yesterday with my better half driving it. the trailers she was pulling weigh in around 13000 kgs. I thought she did pretty good.