need help with my diesel

[Smokinyotes]

I had an 03 Duramax and took it out to sicamous. At the time we had a little 25' vanguard fifth wheel that weighed 5100 dry. I filled up at husky a couple times and noticed a lack of power right away and terrible mileage.

[BlackHeart]

Drove from Edmonton to winnepeg, pulling 8000lbs .....nothing really for the 5.9. Fueled up east side of Saskatoon,......thought I was going to loose my engine. Even the clueless one aboard said something sounds really wrong. Mileage on the overhead, plummeted....reflecting what was happening......barely made it to the next station. Put more fuel in to dilute the crap in the tank. Did this every chance I got. Was afraid to burn it too low.

Every fill up made a major step jump back up to norm. When it started, I thought my engine or injectors were toast. I thought something was wrong when I had a hard time filling the tank due to so much foaming.

Next time through that area, I'm going to VISIT w the station manager. I'm pretty sure its a planned way to make money for them.....just a few obs. thzt had made me go hmmmmm???? But the results confirmed it. "Somebood gonna get hurt!"

[32-40win]

About the only item that doesn't really apply to pickups towing, vs a Class 8 truck towing, is the air compressor, on a unit with air brakes. This article from Cummins does shed some light, on how fuel mileage is affected by various factors, all of them affect any vehicle, that is towing something, to a certain degree. It's worth a read ;

http://cumminsengines.com/uploads/do...el_economy.pdf

[cody c]

Im not sure about the new electronics, but I believe in the past you could adjust the speedo but not the odometer, it may still read based on a 31" tire, and you may be getting around 10% better mileage then what you think you are getting.

Second, your oversized tires are giving you what I like to call rubber overdirve, this effects your gearing at different speeds. The manufacturere has probably figured out what gearing is best for what rpm to get good mileage in an unloaded truck at 100-110 km/hr, now with the larger rubber you'd need to drive at the same RPMyou'd need to be going around 120-130, but at this spped wind resistance plays a bigger part, and couple that with the fact that your pulling a trailer doesnt help, having said that your mileage still really sucks. Try taking it to the dealer to get it checked out or install one of those aftermarket tuners with an economy mode/setting. The 6.7's are notorious for having worse mileage then the 5.9's though, lots of guys say they would prefer their old 5.9 back again.

[AbAngler]

Originally Posted by panamajr

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

Sorry for the late reply.

Your brake controller might be set too high. My nephew was playing in my truck years ago and turned my controller up a bit. Not enough for me to notice or lock them up on pavement, but enough that the trailer brakes were constantly on. Pretty much burnt them out.

Its just another thing to check.

[a little redneck]

I get worse mileage towing to and from Sask. than I do towing in the mountains, or towing to Pincher Creek. This is due to towing in a 45 degree headwind, about the worst type of wind you can tow in, and the winds are usually around 40-50 kph. My overhead is usually 19l/100km towing my cargo trailer (in the city or on the highway) and was 23l/100km in the wind towing to Sask., (950 km trip), which is closer to 25l/100km hand calculated, even with a tuner and deletes. My trailer was loaded and I had a 300 bricks (combination of firebrick and regular bricks), 7 bags of cement and other goodies in the box and the 7X14 cargo trailer was full. If I was towing with the truck box and trailer empty my mileage would be approx. 20-21l/100km on the overhead or 22-23l/100km hand calculated.

I think you may have had bad fuel. The tires won't help but should not make the mileage that bad, has to be the fuel. I'd also check to see that your air filter is not plugged with poplar fluff or dirt. Regeneration is more of an issue in town than on the highway towing.

[buckbrushoutdoors]

Seems brutal to me, I have the exact same truck and lift and tire combo and pulling a 18' trailer with a skid steer and sxs and two quads on it i got 16ltr/100km doing 115km. Biggest differnce is mine has all the deletes done tho.

[jip911]

I have a 2012 megacab and pull a 43' toybox around... it weighs in loaded @ just over 16500lbs...as others have stated speed makes a huge difference.
20l/100km @ 90 km/h
24l/100km @ 100 km/h
26/100km @ 105 km/h
29/100km @ 110 km/h
32/100km @ 115 km/h
36/100km @ 120 km/h

I ended up putting a 225L slip tank in and typically tow at the posted speed limit. Seems to be the best compromise for fuel economy and courtesy to the other people on the road.

I know how much I love getting behind the guys doing 20 under the speedlimit because they can get there 20 bux cheaper...
J

[dodgeboy1979]

i would look at regearing the rearend to a lower ratio

[panamajr]

Originally Posted by gmcmax05

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.

18000 was the second oil change i had done on that truck

[panamajr]

Originally Posted by 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?

ya bud that was me they have my truck in the shop right now and are in awe they have even taken it out themselves towing cant find the issue

[70chevy]

Originally Posted by panamajr

ya bud that was me they have my truck in the shop right now and are in awe they have even taken it out themselves towing cant find the issue

Ok so just a heads up,I was traveling about 122 when u passed me so I think your speedo is out if you thought you were doing 120.You were doing more like 130 +.Hope this helps

[JB_AOL]

Originally Posted by buckbrushoutdoors

Seems brutal to me, I have the exact same truck and lift and tire combo and pulling a 18' trailer with a skid steer and sxs and two quads on it i got 16ltr/100km doing 115km. Biggest differnce is mine has all the deletes done tho.

An open trailer is completely different than an enclosed trailer. Its call surface area..that is bad for mpg.

[Taco]

Originally Posted by 70chevy

Ok so just a heads up,I was traveling about 122 when u passed me so I think your speedo is out if you thought you were doing 120.You were doing more like 130 +.Hope this helps

130 yankin' a holiday trailer is mooovin' on out.........

[hl649]

That sounds about right to me for what you are doing. Let's see, big tires, speed, high speed rearend, pulling large 5th wheel...they all add up to increased fuel consumption. Try slowing down and drive with the overdrive off to bring the revs up. That should help a bit.

I get about 24L/100km pulling a 20,000 lb horse trailer to and from Vancouver. I don't have big tires, I have 4:10 gears, and I drive 90 - 100 km/hr.

[panamajr]

Originally Posted by 70chevy

Ok so just a heads up,I was traveling about 122 when u passed me so I think your speedo is out if you thought you were doing 120.You were doing more like 130 +.Hope this helps

thanx for the heads up i had a gps with me and the dealer set the speedo to the tires. i wouldnt of been going that fast if i new

[Ishpah]

hl649 said, "That sounds about right to me for what you are doing. Let's see, big tires, speed, high speed rearend, pulling large 5th wheel...they all add up to increased fuel consumption. Try slowing down and drive with the overdrive off to bring the revs up. That should help a bit." and I will second that. Also, replace your fuel/water seperator filter more often and make sure your oil level is on the money. You need lots of oil for the high pressure oil pump which drives the injector pump and consider using pure synthetic oil and large capacity oil filter if you can find one for your application. Try Fleetgard. At 130+ you're way beyond your economy sweetspot. Since you are more or less flatlanding, use your cruise control.

[scammed]

Originally Posted by Ishpah

hl649 said, "That sounds about right to me for what you are doing. Let's see, big tires, speed, high speed rearend, pulling large 5th wheel...they all add up to increased fuel consumption. Try slowing down and drive with the overdrive off to bring the revs up. That should help a bit." and I will second that. Also, replace your fuel/water seperator filter more often and make sure your oil level is on the money. You need lots of oil for the high pressure oil pump which drives the injector pump and consider using pure synthetic oil and large capacity oil filter if you can find one for your application. Try Fleetgard. At 130+ you're way beyond your economy sweetspot. Since you are more or less flatlanding, use your cruise control.

cummins

Blame the epa for the mileage issues. These trucks are also almost double the power and much heavier than the mid 90's trucks. They will use more fuel. Doing the deletes will keep the oil visibly cleaner. But the only real way to know if your oil condition is having it analyzed by a lab.

Aerodynamic drag increases exponentially with speed. There are many variables but you could easily see a ~30% improvement in economy with ~20km/h speed reduction.

1000km trip
400L of fuel and 7.69 hours with 3.07 fuel stops $460
280L of fuel and 9.25 hours with 2.15 fuel stops $322

Lets say
40L/100km @130km/h
28L/100km @105km/h

Fuel capacity ~130L
130km/h 325km range
105km/h 464km range

$138 cheaper and 1.5 hours slower (even less if you include the fuel stop time)

So it costs roughly $100 for every hour sooner you want to arrive or $140 of pre-tax income. So it would cost an average person 4-5 hours working to save 1 hour of travel time.