Fuel MPG
 

Im curious what others are getting...


We've been having some discussions and it seem i (mysteriously get good mpg)...admittedly i have a heavy foot, i have been typified (by more than one LEO) as an aggressive driver.

We are 42 feet, single rear axle, MBE 4000 (450hp) and ZF/Meritor 12 speed (manu-matic).

We tip the scale at 36k lbs (moderately loaded w/ fuel & 220g of fresh water), not including the ('12) Jeep Wrangler Sport (2 door soft top) that weighs in around 4200lbs

We consistently obtain 9.9 MPG, and have rarely seen lower than 8.0.

We have seen as high as 13 and change (low speed) secondary roads where we were barely able to maintain 60mph (fog & night driving) from Atlanta to Destin.

Towing 11k lb race/car trailer did not effect or mpg.

The fact the trailer did not effect you tells me your rat end gear is to low.

fuel consumption
 

Don you do go a long way on a gallon of fuel. My rig is much older and smaller. 1982 Peterbilt 359 with a 450 hp Cummins STC (step timing control). The engine is a 1987. I have a 13 speed manual transmission with 336 rear end. I am 30' long and weigh just under 25 K loaded and tow a trailer 7K or Scion XB 2600 lbs. 1500 rpm in 8 th direct gives me 60 mph. My best has been 9.7 and worst 7.8 with an average around 8.8. I am sure that my big square bunk above the cab has bad aero drag and in a head wind I use more fuel. I try to end each trip with a fuel-up at the same fuel pump thinking that I would be more accurate with my fuel use. I don't have a gauge that shows real time fuel use so I run the engine where it feels like it is in a sweet spot.

I've just confirmed our coach came from Freightliner with a 3.21 rear

at 72mph we are turning just under 1500 rpm (sorry for the blurry picture, but all of these were taken w/ the cruise control set, no tricks)

72 MPH -> https://www.truckconversion.net/attac...49606d7746.jpg

65 MPH -> https://www.truckconversion.net/attac...9e745d9d7b.jpg

65 MPH -> https://www.truckconversion.net/attac...a940241450.jpg

I dont understand how you arrived at that, 6k (more lbs) then than jeep wrangler shouldn't really effect us.

a 10k lb trailer that is hidden in the air stream of the coach shouldn't really have any impact imo.

I don't know what my rear end is but I only get 65mph out of 1500 rpm, I have been wanting to get a picture but cant get the gps and the tach together and stay between the paint. I looked in the driver side door jams and did not see a gear ratio just wt info. Here are the pictures of the info I do have.

7 miles to the gal Sam

Been on the internet looking and wondering. Take a look at this, MERCEDES Tuning & Performance | MBE-4000 Highway Truck it deletes your EGR and if you have Def looks like it too. Any one heard of this? What do you think? I have local dealer that I called today and will get a price tomorrow so we can see how this factors into things.

Also my chassis is a 2003 and the RV a 2005. Wonder if that has something to do with mileage?

Sam

Found a pdf on the MBE 4000 performance and Economy here is link.

https://www.google.com/url?sa=t&rct=...Uyq9Kg&cad=rja

Sam

I have twin screw rear and 45 ft length and approx 36K lbs for the coach. Cummins ISX15 and 10 speed Eaton Ultrashift. I typically run 70-72 on interstates, which is about 1550 rpm for me. I think I have 3.36 rear gear, but have not ever really checked for sure. I don't regularly check mileage, but it is around 7 mpg. Mine is not aerodynamic, so I might do better if I drove slower. Usually towing a toad around 4K lbs, sometimes a trailer with car on it around 6K lbs. Toad or trailer does not make much difference in mpg, but can feel it when accelerating from a stop.

My engine has EGR, but no DPF or DEF. I have heard of 10-15% increase in mpg with an EGR delete, but nobody seems to have the real programming figured out to avoid the CEL and getting max performance potential.

47 feet/41K Lbs/8 MPG running 71 MPH

Got the price today on the egr delete, the plug around 50.00 and the programing 2300!!

So, I was told more hp and torque helps on the mileage but just a little??

Sam

I wonder what they can do for non-emissions engines

Sam...you have an 03 engine, does it even have an EGR? My 03 engine (04 coach) does not have EGR.

at that price id want a guarantee!!!

i know any dealer can adjust HP/Tune, I've been thinking (forever) that id go get mine pumped up a little possibly and have then change the default starting gear (i start in 3rd & think i could start off fine in 5th or 6th gear).

id also have them remove the 72mph cruise (set) limit too.

Does the transmission have to be completely reprogrammed if you "tweak" the engine?

If I could have picked up 1.5 mpg on my last trip, I could have made a good down payment on the modifications. A little more shove would not be bad either. I used to be the fastest thing on a mountain with more than 8 wheels, until I got to AK. Those guys up there with the 650hp 18 speeds went by me like paint on a fence...pulling doubles!

NO EGR....so I was having fun for nothing I guess I should have looked under the hood first.

I am going to call the Freightliner dealer in Nashville tomorrow and ask about all that. I have never set my cruise over 70 that I can remember.....didn't know it had a limit.

I have also looked for programmers on line and they ain't cheap either.

Things to wonder about....

Sam

yours might not, but i know mine won't set any higher than 71/72mph (gps verified), speedo indicated 70mph

I think John (aka THUNDERUSONE) had dabbled with a bully dog and someone else, iirc the results weren't great and he returned it....as i also recall it was 800+ for the tuner

hey I'm just here to help you spend your money :D

If your going to spend the money, You should look at gears. . Most HDTs are geared to pull 80k pounds. Our trucks just don't carry that much. Upping the HP will make the engine work a little easier but it takes fuel to make HP.
Find out what RPM peak torque on your engine is and gear your truck to run that at your desired cruising speed You might have to downshift a little earlier on the hills but it will make your life a lot easier.
Rather than comparing engines/tuners/and such, compare top gear ratio/final drive/tire size. Speed is a factor in either case.

I think Freightliner puts the rear end ratio on a sticker on the inside of the fuse box cover? At least I think that's where I found mine.

Just got back from a 2800 mile trip. From Minnesota to Idaho and back. Lots of climbing/descending out there. I was pulling my enclosed trailer with a Honda Pilot in it. The Pilot is 4800 lbs. and my trailer empty is 3k lbs. Plus we threw a bunch of stuff in the trailer. It felt a lot heavier than when we're taking the Corvette to the track. I think I got 7.5 mpg for the lowest and 8.7 for the highest mpg calculations. I always fill up until it clicks off and do the math on paper. My speedometer and odometer are both off since I switched to 11R22.5 tires. They are a bit larger diameter than the original 275/80R/22.5 tires. When I switched to the larger tires it gave me a noticeable reduction in rpm's when cruising. But I also notice my speedo/odo are off. Checking speed with GPS shows when the speedo is showing 65 mph I'm actually going about 67-68. So that means that my miles are off. Which means I'm actually getting better mpg than what my math shows. I'm planning to contact the FL dealer to see if they can adjust my speedo/odo with a computer of something. When I'm cruising at a shown 66-67 mph my rpm's are about 1425-50.

My Speedo is off too and come to think of it, it makes a differents when I put the pencil to the mileage....mmm The speedo is like yours Bob gps 65 and showing 67 68. But I am turning 1500 at 65 gps. I under stand they are dip switches to change the speed. My fuse cover is blank.

Sam

I found a build sheet in my (freight liner) packet -

https://www.truckconversion.net/attac...a83ca3c532.jpg