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Deezl Smoke

Volvo D13 fuel mileage in your rv config?

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 Hi all. It's been a while.

 I finally have had the chance to run a few short trips in my Peterbilt. 20190830_131948_resized.jpg.13d6c0e3ecc77cfe9e56a9ac2201b19b.jpg

 Granted it is way over engined. C-15 @ 550, but the best mpg I have achieved yet is 8.2. That is with no trailer, just as pictured. Singled long, 3.36:1 axle and double over 18 speed. 90% freeway at 60 to 65mph.

 It has been the best fun ever. However, the mpg is getting to be a hang up with me. It's not that I can't afford it, I just don't care to "waste" that much fuel when I know I can have close to the same fun at a much better mpg.

 So here is a truck I am looking at. Granted it will have emission junk on it that I will have to deal with, but it appears to be well suited for the rv application.

 Curious what those of you with the D13 engine, whatever year, are getting in your application. I know most pull a fifth wheel, but still, what is your mpg like? Also any other brand owners, what engine and configuration have you found to get good mpg?

 Thank you.

 Don.

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"I just don't care to "waste" that much fuel when I know I can have close to the same fun at a much better mpg."

I'd be surprised if you can find an HDT that gets "MUCH better mpg".

I think you'll be lucky to hit the VERY LOW double digits (10.0 ~ 10.4). 

I do hope that you can prove me wrong.

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My Freightliner has the DD15 with the Eaton auto shift 10 speed trans, and I just bobtailed to Elkhart to look at the Luxe as I am thinking of ordering one, anyway the millage I got was under 9 mpg. I did run the posted speed limit plus the 5 mph grace, the complete trip, hand figured every fillup and was 8.2 to 8.9. I am set at 560hp and 1850tkq. 

Not the millage my Cummins M-11 got, but not that little motor eather, so is it worth trading truck for better millage, or keep the truck you have and live with it, and I wouldn't trade that Peterbilt off for a Volvo over fuel millage, buts thats just me.

Roger

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Particulars in my signature, but I was disappointed to get less than 9 mpg average.  it's a 12 speed, no overdrive/direct drive.  Like most car owners I had no idea of the different configurations an HDT could be ordered in.  I was reading mostly about the rear end ratio without understanding the trans gearing.   

This is about half mountain, half "flat" driving and almost all bobtail so far.

Edited by Sculptor

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I have a Cummins N14 with an Eaton Autoshift 10 speed transmission.  Mine is a 2000 model year so no emissions gear.  Pulling my 20000 lb +/- 5th wheel, I average 8+ miles per gallon with combined terrain (hills & flat).  If I am all highway in the flats, that will go up to 9+ mpg.  Bobtail, I can get into the low double digits mpg on the highway in the flats, but I rarely run bobtail for any significant distances, so I don't see that very often.  When I was towing my previous 5th wheel, which weighed about 16500 lbs, I was 9+ mpg combined terrain and right around 10+ mpg in the flats.  My engine is set at 460 hp and 1550 ft/lb torque.  I recently had an in-frame done on the motor, which I thought might help my mileage a little, but it didn't make any significant difference.

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2000 Volvo, N-14 @ 460 Autoshift .74 OD  I get 8.9 on a good day here in the northeast. Fiver + Volvo =just under 40K.

Note I changed the rear gears to 3.08 from 3.73.

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1 hour ago, Hewhoknowslittle said:

My Freightliner has the DD15 with the Eaton auto shift 10 speed trans, and I just bobtailed to Elkhart to look at the Luxe as I am thinking of ordering one, anyway the millage I got was under 9 mpg. I did run the posted speed limit plus the 5 mph grace, the complete trip, hand figured every fillup and was 8.2 to 8.9. I am set at 560hp and 1850tkq. 

Not the millage my Cummins M-11 got, but not that little motor eather, so is it worth trading truck for better millage, or keep the truck you have and live with it, and I wouldn't trade that Peterbilt off for a Volvo over fuel millage, buts thats just me.

Roger

 I really do like the 379. It is an X trim, so less than 2,000 were made. By the looks of the replies so far, I wont gain enough to make the switch. I watched Gregg's video on youtube several times and the 11 to 13 average sounds so good. But I can's find anywhere that he mentions using imperial gallons vs. US gallons.

 Thanks for the reply. Love your rig. Looks very refined and thought out.

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Deezl, the only way that you will get 11 to 13 mpg in one of these trucks is when you leave Denver and head to the flatlands and use your "Georgia Overdrive". Unless you want to creep around at 55mph and stay on the flats, most of us will get in the 7.5 to 8.7 mpg range with a 15 liter and maybe 8.3 to 9.1 with a 13 liter running 65 mph or so. I tend to run a little faster so most of the time I am in the 7.6 range with an ISX15.

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What people don't get is your engine is a ( big ) air compressor that needs a ratio of fuel and air to run. The slower it runs in the most distance is the key without load. 1984 Pete 359-3406B 13 speed I don't really need my 3.90 gears but o well.

Edited by beemergary
add ons

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If it helps I get just under 9 with a d11 pulling 13k and I take it easy. I think when I can get it out of the new England mountains and open it up a little on the interstate it will get a little over 9. I got 9.7 bobtailing back from Texas. 

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Our 34' Diesel pusher got 8-8.5 mpg it weight in at 26,000 lbs. Our HDT that is 18,000 and our 45' 5th wheel that is 20,000 gets around at 9 mpg. So we are hella longer, and hella heavier but overall the MPG went up. I cant really complain about that.

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10 minutes ago, Imurphy907 said:

Our 34' Diesel pusher got 8-8.5 mpg it weight in at 26,000 lbs. Our HDT that is 18,000 and our 45' 5th wheel that is 20,000 gets around at 9 mpg. So we are hella longer, and hella heavier but overall the MPG went up. I cant really complain about that.

Most of those pushers push a lot of air. I was told, at a bus training years ago, that a bus uses 40 hp to push the air at 60. They also said that a Cadillac only used 12 horsepower to maintain 60 on flat going. I have no idea if the instructor was correct or not, but just try to hold a piece of plywood up in a strong breeze, say nothing about getting it up to road speed. I would think you hdt is more aerodynamic, also weight at speed is not that hard to pull until you add gravity.

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I like the D13 for various reasons like it’s a tough engine. But mainly I like the fuel economy I am geeting. A lot of that has to do with mating up with the Volvo I-Shift. That’s a pretty unbeatable package right there. Its really make me happy.

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2 hours ago, Imurphy907 said:

Our 34' Diesel pusher got 8-8.5 mpg it weight in at 26,000 lbs. Our HDT that is 18,000 and our 45' 5th wheel that is 20,000 gets around at 9 mpg. So we are hella longer, and hella heavier but overall the MPG went up. I cant really complain about that.

 Awesome information. Thank you. I wondered about the fuel use of a flat nose MH.

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My truck has a C13 and 3.70's same final drive ratio and set at 500/1750       It IS an aero truck with a single rear axle that is pretty light 16K .      Bobtail I see anywhere from 12-8 depending on how fast I drive.     Towing my 48' trailer 25K I get 9-6 depending on how fast I drive.   

 

The best MPG numbers are at 65 the worst are at 75-80 plus.

 

Steve

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My truck and fifth wheel weigh 35,800 LBS and gear ratio 3.55 Volvo D13 with 13 speed manual. we get 6.5 to 8.5 mpg at 65 mph @1400 rpms  at 70 mph about 1 to 1.5 lower mpg @1600 rpms.

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Bobtail with just the smart car on the back of our Freightliner Century with a Detroit 14l, Ultrashift 10 speed and 3:55 gears, I saw just under 11 mpg at one fill up and in the 9 & 10's on the other two from South Carolina. With our old trailer at about 23k# we got about 7-9 mpg. Most of the issue with the trailer is the large gap between the truck and trailer. For a few years we closed that gap up and got an extra mpg. You are probably losing some MPG because you do not have an aero truck and your rear end gearing. If you can buy new and spec one out with what would work for your loads you could probably improve mileage into the double digits but you probably would also have a large truck payment too. It is all about compromise.

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2 hours ago, Star Dreamer said:

Bobtail with just the smart car on the back of our Freightliner Century with a Detroit 14l, Ultrashift 10 speed and 3:55 gears, I saw just under 11 mpg at one fill up and in the 9 & 10's on the other two from South Carolina. With our old trailer at about 23k# we got about 7-9 mpg. Most of the issue with the trailer is the large gap between the truck and trailer. For a few years we closed that gap up and got an extra mpg. You are probably losing some MPG because you do not have an aero truck and your rear end gearing. If you can buy new and spec one out with what would work for your loads you could probably improve mileage into the double digits but you probably would also have a large truck payment too. It is all about compromise.

 Awesome info. Thank you. Yes, I am basically pushing a brick. I have been looking at the aero volvos, hence this thread. I have found more 6x2 drive configurations lately. I think that would fit my purpose well with a 2.6 axle. I see some people that use the dash mpg meter, are showing 15-16 when bobtailing  longer distances and when already up to highway speed. I'd be a happy camper with 10.

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Howdy Deezl Smoke,

I also have a C-15, 550hp-1850t, 3.55 axles, 18 speed Auto-Shift.  Truck with deck and Smart Car is around 22,000 pounds, trailer is around 19,000 / 21,000 depending on which or how many toys I have in the box.  I have never gotten worse then 6mpg or more then 7.5mpg average on trips of 2,000 miles, usually more miles I tend to do long trips of 5,000 miles or more, I can't go anywhere without crossing mountain ranges. 

I got about a mile better fuel mileage with the Freightliner I had before I built the Pete, the Freightliner had a 12.7 DD, 10 speed Auto-Shift and 3.55 axle, in a purely practical sense the Freightliner was a better truck for RV use, it was shorter, weighed less, and was singled, but when it comes to climbing mountains while carrying the Smart Car on the deck and towing that big trailer, the SMILE the big Cat puts on my face is priceless and I wouldn't trade it for another mile per gallon. At my age my truck is a big toy and I enjoy playing with it, yeah I know I am going to HELL for causing the planet to burn up and destroy the lives of future children, oh well.

Dave

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16 minutes ago, mr. cob said:

Howdy Deezl Smoke,

I also have a C-15, 550hp-1850t, 3.55 axles, 18 speed Auto-Shift.  Truck with deck and Smart Car is around 22,000 pounds, trailer is around 19,000 / 21,000 depending on which or how many toys I have in the box.  I have never gotten worse then 6mpg or more then 7.5mpg average on trips of 2,000 miles, usually more miles I tend to do long trips of 5,000 miles or more, I can't go anywhere without crossing mountain ranges. 

I got about a mile better fuel mileage with the Freightliner I had before I built the Pete, the Freightliner had a 12.7 DD, 10 speed Auto-Shift and 3.55 axle, in a purely practical sense the Freightliner was a better truck for RV use, it was shorter, weighed less, and was singled, but when it comes to climbing mountains while carrying the Smart Car on the deck and towing that big trailer, the SMILE the big Cat puts on my face is priceless and I wouldn't trade it for another mile per gallon. At my age my truck is a big toy and I enjoy playing with it, yeah I know I am going to HELL for causing the planet to burn up and destroy the lives of future children, oh well.

Dave

 OH YA !!! Well said. That "smile" is ever so priceless. Just set cruise and no hill can stand in it's way.

 Thank you very much for the reply. I feel better about my mileage already.

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