400 Cummins mileage help

highcountry · 03-11-2012, 06:55 PM

I have a 07 Winnebago Tour 40FD. I tow a 02 Jeep Liberty. I can only muster about 6 MPG @62MPH. I have had other DP's and have always managed to get between 8-10 including an Eagle which was much heavier. I have talked to Cummins and they want to put it on a Dyno at a cost of 4-500. Anyone have any experience with this? Would I be better off spending the money on a chip or Fans, or breathers, or, or, or?

bdaball · 03-11-2012, 07:01 PM

Quote:

Originally Posted by highcountry

I have a 07 Winnebago Tour 40FD. I tow a 02 Jeep Liberty. I can only muster about 6 MPG @62MPH. I have had other DP's and have always managed to get between 8-10 including an Eagle which was much heavier. I have talked to Cummins and they want to put it on a Dyno at a cost of 4-500. Anyone have any experience with this? Would I be better off spending the money on a chip or Fans, or breathers, or, or, or?

Welcome Highcountry,
Regardless of the feedback you get here, don't forget to log on to the Freightliner Chat room every Wednesday evening at 9PM EST/DLST. You will meet a great bunch of freightliner guys who have answers to anything you could ever imagine. Well almost everything.

And the best part it is free.........!

bluepill · 03-11-2012, 07:16 PM

some thoughts:

1. check your brake rotor/drum temps on both the MH and the toad with an IR thermometer after driving at speed with little brake usage for 20 minutes or more. Any high reading indicates drag.

2. Monitor your transmission shift pattern for abnormal shift points. If your trans has a selection of power and economy, use the economy mode.

3. Don't forget that onboard diesel generator use increases consumption.

4. Make sure that the coolant temperature comes up to normal (180-190 deg.) fairly quickly (5-10 minutes of driving)

5. A radiator fan that stays in High Cooling mode uses as much as 75 horsepower.

highcountry · 03-11-2012, 07:20 PM

As an old truck driver, I do check the heat of the tires/hubs by hand. The tranny seems to shift very well. I do use the econo mode. Thanks

RVThere · 03-11-2012, 08:28 PM

I have a 2007 Tour 40TD with the 400 hp Cummins and your mileage is right in line with what I have been getting for close to 50K miles pulling a Jeep GC.

When I see 7 mpg (with a tail wind going down hill), I jump for joy!

Petro · 03-12-2012, 06:16 PM

Quote:

Originally Posted by highcountry

I have a 07 Winnebago Tour 40FD. I tow a 02 Jeep Liberty. I can only muster about 6 MPG @62MPH. I have had other DP's and have always managed to get between 8-10 including an Eagle which was much heavier. I have talked to Cummins and they want to put it on a Dyno at a cost of 4-500. Anyone have any experience with this? Would I be better off spending the money on a chip or Fans, or breathers, or, or, or?

I am doing about the same as you. If I get 7.5 MPG I jump for joy. Normally 6.5 -7 is about average. My thoughts are that the more horses we have the more they eat.

bdaball gave you good advice. Join us on the Freightliner Chat on Wednesday nights. It is time well spent.

Don

rv rick · 03-12-2012, 06:44 PM

I had a 2008 40' TD Tour with the 400 and averaged 8.1 for 35,000 miles towing a Chev. HHR. I usually drove at about 58mph and noticed a big difference in mileage driving at 57-58 and 62-64.

Interestingly, I get over 8.5 in our 2010 42' Tour AD with the tag axle (over 12,000 miles so far). This is a heavier rig and does not have the urea injection. I have noticed that the transmission program shifts into 6th at a lower rpm than the 40TD did.

Mr_D · 03-12-2012, 06:53 PM

Does seem kind of low. Our ISC 350 (now 435/1200 with the Banks kit) gets 7.5 to 8 overall (incl gen usage). On my VMSpc and the flats I can see 14-16mpg and 3 mpg going up some hills or 70 mph into a very stiff headwind. I also see 256 mpg going down hills. Take your pick!!

Ralph A · 03-12-2012, 07:18 PM

I'm getting a good solid 8.5 mpg with my 2005 Horizon AD40 & 400 hp Cummins now towing a 2011 Jeep Wrangler Unlimited but was towing a 2005 Honda CRV. I have 75,000 miles on the rig; about 70,000 towing the Honda and 5,000 with the Jeep in tow. My last 5,000 with the Jeep averaged 8.38 mpg. I drive the speed limits not to exceed 75 mph. I have always used a diesel additive. These are actual mpg readings, not the readings off the Information Center which usually show about a 9.0 range.

kjburns · 03-13-2012, 02:36 AM

Quote:

Originally Posted by rv rick

I had a 2008 40' TD Tour with the 400 and averaged 8.1 for 35,000 miles towing a Chev. HHR. I usually drove at about 58mph and noticed a big difference in mileage driving at 57-58 and 62-64.

We had exactly the same (8.1 mpg) showing on our trip computer, towing a 2010 Grand Cherokee. I don't know how accurate the computer is and didn't verify the results, but it's probably accurate within a few percentage points.

cardiffman · 03-13-2012, 10:24 AM

Here is my $.02 worth: After 10 years and 50,000 miles on a Country Coach 350 Cummins, I don't think I ever say the good side of 7 MPG. Mostly in the 6's. There is a good old adage: "There are two things a man will lie about. One is gas mileage" Frankly, I think most mileage guestimates come from the gauges, and some come from wishful thinking. The only way to know for sure is the old fashioned way of filling the tank and calculating by pencil (or pen). My VMS engine monitor always read higher than actual. The factory installed calculator was off nearly 2 MPG.

When you consider your driving habits plus terrain and wind, the variables go up. These dang things just aren't built for mileage are they? Don't ya just love em?