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So on our trip, really bad milage dmax

blazinzuk

blazinzuk

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Not sure if it's bad or not got 9.5 towing 70 to 75 higher elevation up and down some grades wind blowing.

Towing a 27 ft 5th wheel.

From Cheyenne Wyoming to Big springs Nebraska I got 8.4

Strong cross wind most of the way but only doing 60 to 70.

I was hoping for 12 also this truck compared to others really seems down on power.

No check engine light. I checked the air filter, it's not new but decent. Will get a new one tonight.

If anyone is around Kansas city tonight that thinks they might have an idea what's going on lemme know.

I have checked all the normal stuff ya know plugs wires cap rotor:rotfl::rotfl:.

Seriously I am not seeing an issue. It's an 01 extended cab 3/4 ton
 
Dirty maf? That seems low. Most guys I know pull no less than 12 with huge 5ths. Down on power while towing is usually a collapsed fuel line. Usually by the driver side rear valve cover or under the tank by the trans. Does the truck have a lift pump?


Also the filter housings leak and can suck in air. If you hit the shrader valve and fuel comes out foamy it's probably air in the line or collapsed line. If the truck has power when cold the. Falls on its face when warm that's the issue. If not it's a weak cp3.


Even with collapsed lines last year I still pulled 15mpg
 
Down to 8.2 mpg on flat ground through Nebraska on I80 light winds 75 mph
 
blazinzuk said:
Not sure if it's bad or not got 9.5 towing 70 to 75 higher elevation up and down some grades wind blowing.

Towing a 27 ft 5th wheel.

From Cheyenne Wyoming to Big springs Nebraska I got 8.4

Strong cross wind most of the way but only doing 60 to 70.

I was hoping for 12 also this truck compared to others really seems down on power.

No check engine light. I checked the air filter, it's not new but decent. Will get a new one tonight.

If anyone is around Kansas city tonight that thinks they might have an idea what's going on lemme know.

I have checked all the normal stuff ya know plugs wires cap rotor:rotfl::rotfl:.

Seriously I am not seeing an issue. It's an 01 extended cab 3/4 ton
Click to expand...

05' Dmax and I count on 10 mpg with a popup cab over and buggy behind it. I've eliminated every power robing and fuel eating thing I can, 4" exhaust from an earlier version truck so no Cat, EGR is sitting on a shelf, PCV re-routed etc. I've seen south of 10 several times when I was pulling a high profile trailer and trying to haul too much ass. My trucks happy spot is at 72 MPH, higher and the mileage drops, lower and the power suffers to the point that it causes heavy throttle input on hills and drops the mileage.

While I would "expect" you should be getting 10 to 12 mpg, I'm guessing that you have a high profile 5th wheel RV trailer and it's like towing a brick wall above the roof of the truck and it's introducing so much aerodynamic drag that you are feeling down on power and mileage. When I was trying to figure out how to make my truck get the famous 15+ mpg towing I read a lot of info and came to the conclusion that at speeds over 55 MPH the major thing your fighting is aerodynamics.

Slow your ass down or get a bigger fuel tank.
 
You can really tell a huge difference between 60 and 75 when your on a bike.....multiply that times 50 for a truck/Rv combo
 
I was looking at the old records for the Cummins and it had gotten an average of 14,19 pulling a 7100 LB camper at 60 MPH.

(94 12 valve 2wd 5 speed)
 
Slowed down to between 65 and 70. Went up! From 8.2 to 8.5.

@miniwally I don't wanna slow down.

Btw it seems way down on power at 65 it's downshifting for any incline.
 
I had an air cleaner compress down once. Milage went in the tank and HP went away. Thought the turbo was imploding.

So every time either started going down, I checked it and cleaned it. Issue resolved.

But as speed went up, economy went down.
 
1977k5 said:
How old are the injectors?
Click to expand...

with the mileage he is getting I would expect it to be hazing every time he stopped or slowed down if it was injectors. When I talked to him earlier it didn't sound like anything was out of the ordinary except poor mileage and no power.

The lb7's don't through codes like the newer trucks.
 
speed costs gas Eric. Its amazing how much more diesel my dodge burns at 85 than 75. I drop 3 miles a gallon trying to run at 85
 
Ok finally got to Kansas city.

Last tank 9.7

Speed was 55 to 65. Most of it around 60.

I realize the aerodynamic issue. I was hoping for 12.

But in over a thousand miles of driving I haven't broke 10

@jekquistk5 Jesse oh no man we got here at midnight. Been on the road since 9 am. Besides the pouring rain issue. I'm going to bed.

Also thanks tons for the suggestions guys. It really does feel down in power. I will report back when I get a new air filter and fuel filter.
 
1977k5 said:
How old are the injectors?
Click to expand...
120k ? Maybe? That was my first thought too but nothing I can do about that right now

Really the biggest issue is this is like taking a brand new[ used ( to me)] truck. Driving it for 10 minutes and leaving on a road trip. My in laws never actually calculated milage before. I got nothing to compare it too. Every mantainence question I ask they have no clue. Like literally every question.

It's frustrating but to hell with it I'm gonna enjoy my trip.
 
yeah..just relax and have a good time...Its not like your in Baker City asking the dealer what he has on the lot, cause your injector pump just blew out the injection system and BB starts in two days.
 
my buddy just had to do injectors / lines / gaskets on his first gen dmax engine.

he was getting fuel in the crank case . 550 mile trip it grew over 3 qrt of full on the dip stick .

the tapered seats on the lines and injectors were pitted bad from rust that looks to of been caused from water creaping down the line/nut body over the years .

so possibly check you oil level to make sure its nice and black and not over full.
 
I have been checking oil nice and black. Smells like oil. Nothing else.

Trans fluid is good too no burnt.
 
I wonder about the fuel itself...thinner diesel like #1 or kerosene will reduce mpg and produce less power due to lower BTU content..who knows whats in those tanks at many fuel stations ?..maybe some diesel power kleen wont hurt--some guys I know claim adding a quart of SAE 30 oil to each tankfull helps both power and mileage in warmer weather...

I'm not at all familiar with Duramax diesels..I know if the injector pump timing is off it can reduce power and mpg,but that truck probably has that all controlled electronically ?..

Lately my 6.2 smells like I'm burning road tar in it,on a warm day..fuel smells "asphalty" instead of the typical fuel oil smell..also it has been idling a bit rougher than usual,like a sticky valve kind of an irregular misfire,that goes away above idle..probably the fuel I'm getting at the station with the lowest prices..Its overdue for a fuel filter and I should dump some additive in it..
 
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