NoDirectionHome Posted November 26, 2017 Report Share Posted November 26, 2017 As always, great real world insight beyerjf. Quote "There are No Experts, Do the Math!" 2014 Freightliner Cascadia DD16 600hp 1850ft-lb 18spd 3.31 260"wb SpaceCraft S-470 SKP #131740 Link to comment Share on other sites More sharing options...
VegasFlyer Posted November 28, 2017 Report Share Posted November 28, 2017 With a Volvo 780, the weight of your foot can also greatly reflect a big change to the mpg readings. Quote John Southern Nevada 2008 Volvo 780, D13, I-Shift 2017 Keystone Fuzion 420 Toyhauler 2017 Can-Am Maverick X3-RS Link to comment Share on other sites More sharing options...
Rotorhead Posted January 25, 2022 Report Share Posted January 25, 2022 I have started to check and see what I get running BT. So far it appears to be 4.4 mpg. I haven't driven it far between fill ups so I don't know how accurate that is. My question is, if it is accurate what would that mean? Do I have an issue that is causing poor mileage? Injector(s) maybe? Chuck Quote Link to comment Share on other sites More sharing options...
Rotorhead Posted January 25, 2022 Report Share Posted January 25, 2022 On 11/28/2017 at 12:36 AM, VegasFlyer said: With a Volvo 780, the weight of your foot can also greatly reflect a big change to the mpg readings. Hi, I have a 2010 780 with a cummins ISX 15. I think my mileage is about 4.4 bobtail. I need to verify it with more miles between fill ups. But if that is correct is there something I may need to have fixed to get it up to where it should be? Chuck Quote Link to comment Share on other sites More sharing options...
Randyretired Posted January 25, 2022 Report Share Posted January 25, 2022 I don't bobtail much but the couple of times I did it was 12mpg. 2001 ISX. Quote Randy 2001 Volvo VNL 42 Cummins ISX Autoshift Link to comment Share on other sites More sharing options...
Rotorhead Posted January 25, 2022 Report Share Posted January 25, 2022 37 minutes ago, Randyretired said: I don't bobtail much but the couple of times I did it was 12mpg. 2001 ISX. That's way better than I am probably getting. I am going to verify over the next few days. I am trying to get it in for a tune up/valve adjustments but everyone is behind or short handed due to COVID. Quote Link to comment Share on other sites More sharing options...
Steve from SoCal Posted January 25, 2022 Report Share Posted January 25, 2022 That is terrible fuel consumption for a regular tractor even under load. Are you sure the fuel consumption numbers are correct? The only accurate way to check is with actual fuel usage. If the truck is using that much fuel is the engine burning it or is there other sources of use? The DPF has an injector, are the fuel/return lines leaking, is the oil diluted with fuel? That kind of fuel consumption would be the engine under 70+ percent load all the time, is there a driveline issue? Does the truck coast freely or slowdown rapidly when you back off the pedal? Something is way out of wack to have that kind of mileage bobtail. What speed and wind conditions were these numbers derived from? Steve Quote 2005 Peterbilt 387-112 Baby Cat 9 speed U-shift 1996/2016 remod Teton Royal Atlanta 1996 Kentucky 48 single drop stacker garage project Pulls like a train, sounds like a plane....faster than a Cheetah sniffin cocaine. Link to comment Share on other sites More sharing options...
Rotorhead Posted January 25, 2022 Report Share Posted January 25, 2022 26 minutes ago, Steve from SoCal said: That is terrible fuel consumption for a regular tractor even under load. Are you sure the fuel consumption numbers are correct? The only accurate way to check is with actual fuel usage. If the truck is using that much fuel is the engine burning it or is there other sources of use? The DPF has an injector, are the fuel/return lines leaking, is the oil diluted with fuel? That kind of fuel consumption would be the engine under 70+ percent load all the time, is there a driveline issue? Does the truck coast freely or slowdown rapidly when you back off the pedal? Something is way out of wack to have that kind of mileage bobtail. What speed and wind conditions were these numbers derived from? Steve I am going to double check the numbers over the next few days. I have not seen any fuel leaks or any other leaks. The last oil sample the fuel dilution was 1.6% GC (not sure what GC is). It was 0.6% on the first sample about 1800 miles previously. I had just gotten the truck last summer used and wanted to see where it sat on the analysis. I have just taken another sample at 5000 miles since I've gotten it. I won't have those results back for a week or so. I did replace the center bearing and front u-joint. Haven't really driven it in terrible winds. It coasts pretty good when you let off the pedal. If the fuel dilution is up on the next sample I am assuming at least one of the injectors may be bad?? I have the injector leak test tool but haven't gotten around to checking yet. I don't drive it for hundreds of miles at a time. So I suspect that may have something to do with it. I am going to put a couple hundred on it and refill and do the math again. I am also putting a new MAP sensor on. It is still the original and the truck has 892,000 miles. That may be part of it too. She's old and in need of some TLC(aka$$$). haha Quote Link to comment Share on other sites More sharing options...
aknavy Posted January 26, 2022 Report Share Posted January 26, 2022 14 hours ago, Rotorhead said: I have started to check and see what I get running BT. So far it appears to be 4.4 mpg. I haven't driven it far between fill ups so I don't know how accurate that is. My question is, if it is accurate what would that mean? Do I have an issue that is causing poor mileage? Injector(s) maybe? Chuck Man, I thought I was sucking towing 30k with my 2001 660/D12/Eaton Autoshift. Loaded, running around out west in and out of the mountains, I'm getting about 6 mpg. Bobtail, the little that I do it, the lie-o-meter puts me above 10 mpg. So I'd say that's accurate to +/- 1 mpg. Probably + if I'm telling someone and - if I'm paying the fuel bill. I agree with the others, something is amiss. Quote 2001 VNL 660 2018 DRV Fullhouse JX450 2018 Jeep Wrangler Rubicon Link to comment Share on other sites More sharing options...
GlennWest Posted January 26, 2022 Report Share Posted January 26, 2022 I might get 1 mpg more bobtail. Very little difference. I get around 8. Quote 2003 Teton Grand Freedom towed with 2006 Freightliner Century 120 across the beautiful USA welding pipe.https://photos.app.goo.gl/O32ZjgzSzgK7LAyt1 Link to comment Share on other sites More sharing options...
Rotorhead Posted January 26, 2022 Report Share Posted January 26, 2022 8 hours ago, aknavy said: Man, I thought I was sucking towing 30k with my 2001 660/D12/Eaton Autoshift. Loaded, running around out west in and out of the mountains, I'm getting about 6 mpg. Bobtail, the little that I do it, the lie-o-meter puts me above 10 mpg. So I'd say that's accurate to +/- 1 mpg. Probably + if I'm telling someone and - if I'm paying the fuel bill. I agree with the others, something is amiss. As you call it, "lie-o-meter". Mine says 10.1 most of the time. I will be putting more miles on it today and tomorrow and then filling up and checking those real numbers. Quote Link to comment Share on other sites More sharing options...
GlennWest Posted January 26, 2022 Report Share Posted January 26, 2022 My lie o meter on my Freightshaker is a scale of plus and minus scales. Is set at 7 mpg. It stays in plus side unless climbing a hill. When bobtail it pegs out on plus side. I find it difficult to gauge from fuel burned. Just can't get same amount in it. Reckon I could take time and fill until it almost runs over on each side but just don't have the patience. Quote 2003 Teton Grand Freedom towed with 2006 Freightliner Century 120 across the beautiful USA welding pipe.https://photos.app.goo.gl/O32ZjgzSzgK7LAyt1 Link to comment Share on other sites More sharing options...
Rotorhead Posted January 26, 2022 Report Share Posted January 26, 2022 On 11/28/2017 at 12:36 AM, VegasFlyer said: With a Volvo 780, the weight of your foot can also greatly reflect a big change to the mpg readings. Hello VegasFlyer, I was wondering where you get and update the U.S. map for your travels? I did not see it on the ticker site. Chuck Quote Link to comment Share on other sites More sharing options...
Rotorhead Posted January 27, 2022 Report Share Posted January 27, 2022 So with the real numbers I have come up with 6.2 MPG. That was with a mix of highway and city. It still may not be accurate though. I had to do a parked REGEN after I got to work. Anyway, I think it could be better but at least it isn't 4.4. Quote Link to comment Share on other sites More sharing options...
rickeieio Posted January 28, 2022 Report Share Posted January 28, 2022 In another thread, you mention running Jet A. Isn't that a lot like kerosene, with less btu's than regular diesel? Bingo, less btu=less mpg. Quote KW T-680, POPEMOBILE Newmar X-Aire, VATICAN Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row Young enough to play in the dirt as a retired farmer. contact me at rickeieio1@comcast.net Link to comment Share on other sites More sharing options...
lappir Posted January 29, 2022 Report Share Posted January 29, 2022 20 hours ago, rickeieio said: In another thread, you mention running Jet A. Isn't that a lot like kerosene, with less btu's than regular diesel? Bingo, less btu=less mpg. "Jet Fuel", sounds powerful right !!! It is in the right circumstances, very powerful. When I was much younger and my Father was an "Oil Jobber" I asked him why we didn't sell "Jet Fuel" to the farmers instead of the "Number Two" fuel and why we hardly sold any "Number One" except in the winter. I don't remember his exact words, but it was something about when the crude oil was refined and I don't remember the other numbers. (Google it maybe). Number two was the third to last in quality. Number One was just above "Jet Fuel" he called the left overs from the refining of oil, without much of the needed lubrication properties of a diesel motor. I'm sure he went on with other stuff, but I'm now probably at the age he was when I asked him the question and didn't chose being an "Oil Jobber" as my career. Rod Quote White 2000/2010Volvo VNL 770 with 7' Drom box with opposing doors, JOST slider hitch. 600 HP Cummins Signature 18 Speed three pedal auto shift. 1999 Isuzu VehiCross retired to a sticks and bricks garage. Brought out of storage the summer of 2022 2022 Jeep Wrangler Sport S Two door hard top. 2007 Honda GL 1800 2013 Space Craft Mfg S420 Custom built Toyhauler The Gold Volvo is still running and being emptied in July. Link to comment Share on other sites More sharing options...
Deezl Smoke Posted January 29, 2022 Report Share Posted January 29, 2022 Wash the back of your sleepers, then bobtail over a highway with wet spots in the shade etc., and see what the back of your sleeper looks like. That vertical wall sucks more stuff up off the road than the open tires can throw up there. Bobtail mileage depends so much on detail. If you have side fairings, full fenders over the rear, a bed or even a drom box, all make a difference in how that low pressure suction behind the sleeper reacts. Even the front bumper height off the surface makes a difference, as it determines how much air goes under the truck vs. around the outside. It would be good to know everyone's elevation average as well. Driving in the rain takes power. Driving in 110F looses power, etc. Quote I'm a work'n on it. Link to comment Share on other sites More sharing options...
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