Detroit Diesel, 06 515 HP fuel mileage

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Moving on Down the Road, May 7, 2010.

  1. Moving on Down the Road

    Moving on Down the Road Light Load Member

    Mar 6, 2010
    We used to own a 2000 DDEC 12-liter, 430 HP in W900L pulling 53/102 dry box. KW ECM showed high 7's for fuel mileage. The best I ever did was 8.4. Looking at buying 2006 FTL Coronado high-rise condo, 18-spd, 3:58 and L/P lo-pro 22.5 and 53 dry box. Normally like to run 5 MPH below interstate speed limit and all east of Texas. Curious as to REAL fuel mileage expectations, if any of you have good experience with pre-07 DDEC motors. Thanks guys.....​
  2. Captain Canuck

    Captain Canuck "Captain of the Ship"

    Apr 7, 2007
    Woodstock, NB, Canada
    The 14 litre doesn't do quite as well.... still, I'd guess that low 7s would not be unreasonable. With an 18 and 3.58s it's pretty well geared to run 65 unless it's a double overdrive, and might actually do worse if you slow down without running in direct.
  3. losttrucker

    losttrucker Road Train Member

    Mar 9, 2008

    With all the egr crap compared to that 2000 you will be lucky to get 6.5.............I have an '05 mid-roof columbia with a 10speed and 3:55 gears and run 62-63mph, idle NONE and with the pittsburgh power muffler grossin 76k i can get about 6.6
  4. lovesthedrive

    lovesthedrive The Confuzeled

    Nov 11, 2008
    Sorrento, Maine
    10 Speeds wont get the mpg of a 13/18 speed. I drove a 10 columbiaa and got terrible mileage. No thankyou. The truck I am looking at now has a 13 and should put me in the mid 7's in a century. I drove Century's for CR England with a 13, had no problem getting 7.6 with a load. Most of them were 500 hp. For that matter here is the specs of what I am looking at.

    2006 Century

    Cab TypeConvConfiguration
    TRACTORSleeper Size70"
    Sleeper Type
    8GVW52,000 lbs.
    EngineDET 6014.0 515
    Engine Brake
    TransmissionFULLR RTLO-16913A
    Transmission Type
    Transmission Speed13

    Front AxleMBA-F12-3N
    Front Axle SetbackYES
    Front Axle WR
    Rear AxleMRCBNRear
    Axle Type
    Rear Axle Ratio
    Rear Axle WR40,000 lbs.
    Wheelbase 229"
    Fuel TypeDIESEL
    Fuel Tanks Count 2
    Fuel Capacity
    FRGHT Suspension ModelFA240000
    Suspension Type

    5th WheelAIR SLIDE
    Front Wheel Type ALUMINUM
    Rear Wheel TypeALUMINUM
    BBC/Cab Length
    Roof Fairing
    NO Side FairingPartBody
    Exterior ColorMED RED
    Interior TypeSTANDARDInterior ColorGRAPHITE BLACK
    AC YES
    Mileage Adj Price $ 37,250
  5. losttrucker

    losttrucker Road Train Member

    Mar 9, 2008
    Ok its the only difference between a 13sp and 10 sp is less of a difference between 9th and 10th gears unless you spend all your time pulling hills. A 13sp/18sp doesnt affect fuel mileage because the final ratio is about the same as a 10 speed being about .86 ratio and an 18speed is really only good for heavy haul. As far as 500hp motors well Detroit made improvments from the 05,06 14L to newer versions hence the better fuel economy on those engines.

    And as far as those spec's you may wanna do some research as that was a 9sp transmission converted to 13sp and the only benefit to switching it to a 13sp is resale value according to you would be better of having a 10 speed and running it in Direct drive then that 13sp with a final .73 but hey what do I know it's early and I haven't had coffee yet lmao
  6. superhauler

    superhauler Super Crusty

    Jan 30, 2010
    13 or 10 or 18 or whatever it dont matter im not a trans expert but the gear ratio in the rears is what you need to figure out to match the directdrive gear in the trans. if you want to pull a hill like there is no tomorow then gear low and sacrafice mpg. if you want mpg gear high and sacrafice power in the hills. i have a 16913 with 3.70s behind about 650 hp grossing an average of 126000 to 132000 and average 4.4 empty runing 65 i only get 6.2 at the best. but i set it up to pull a hill.
    losttrucker Thanks this.
  7. JohnP3

    JohnP3 Road Train Member

    Feb 21, 2010
    Rock Creek B.C. Canada
    I am no transmission expert but the benefit of running an 18 speed is you have 300 RPM between shifts. It gives you the ability to run at a more constant RPM. Just a thought!
    7mouths2feed and losttrucker Thank this.
  8. Cowpie1

    Cowpie1 Road Train Member

    Nov 25, 2008
    Kellogg, IA
    True, but you get that with a 13 on the top side. The low side has a small spread anyway so there is no reason to go with a heavier 18 unless you are doing specialty work. The only larger split you have is between 5th and 6th going from low range to high.

    The truck listing showed 3.42 rears. I have that ratio in my truck now and have a love/hate relationship with it. In most cases, it is a fine ratio. But overall, based on my loads and runs, I would be much happier with 3.55 or 3.58. I usually have to split down to 12 with the 3.42 rears to keep from lugging once I run below 60mph. With 3.42, 1400 rpm will put you right on 65 mph, 1300 gives you 60 mph, give or take depending on the tires. 1400 in 12th will give you 55 mph. That is also is with a .73 final ratio in my 13 spd. In 12th, I have .86 ratio, direct in 11th.

    Overall, I usually average around 7 mpg year round, a little less in winter, more in summer. Generally running average of 70,000 lb and doing a high percentage of two lane, rolling hill roads.

    That '06 is spec'd pretty well for general freight. You should be able to negotiate the price down somewhat. On the surface, seems like a decent working truck. But, like most things nowadays, it needs to be researched out well to reduce the risk of getting a lemon.
    Last edited: May 13, 2010
  9. Freedom freight

    Freedom freight Bobtail Member

    Mar 11, 2016
    I have an 06 centry with a detroit 60 515 hp 10 speed. Not exactly sure what the gear ratio is. I only average 4.5 to 5.5 mpg loaded. Depends on the terrain obviously. It just simply will not pull a hill loaded and cant keep steady climbing empty. Should i look into the motor or tranny first? Ive had issues with the egr valve and cooler no surprise. Ive had people suggest vpod, turbo and injectors. Motor seems to run strong but just lacks power. This is my first tryck and im still trying to learn about them. Sometimes when excellerating it will cough and spit black smoke but only in 9-10 gear and at around 1200 rpm. Does anyone have a clue as to where i should start? Engine or tranny or both? Fuel mileage is just wearing me out and cutting into my proffits.
  10. Cowpie1

    Cowpie1 Road Train Member

    Nov 25, 2008
    Kellogg, IA
    I took a FL Columbia with a S60, 10 spd, and 3.42 rears out for the owner of the carrier I am with to see what kind of mpg I could get out of it for a couple of months running. I was able to get about 7.3 mpg average from it. Dry box work with everything from 15K to 46K in the box with average around 35K. But I hated the 3.42,ratio. Feel I could have got better with 3.55.
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