MPG @ 55 to 60 MPH - Montana Owners Club

H. John Kohl · 08-31-2007, 02:41 PM

Ann and I made a trip to NY this week. I intentionally drove the speed limit and no more then 60 on the interstate. Going up I got 11.9 and coming back I got 12.2. Also when pulling the hills I did not run the boost over 20 PSI 28 is max for my set up.
Normally when I am pushing the hills and and towing the speed limit I get about 10.5 to NY and back.
I read a post by Cummins that 55 is the turn over number from rolling resistance to wind resistance. These numbers help make a believer out of me.
Cheers,

stiles watson · 08-31-2007, 03:26 PM

John,

With diesel priced as it is, we all need to drive smarter. Thanks for your realistic report. With new diesel emissions standards, we will all be having to pay through the nose. Like I say, for me, it is culture shock.

Mudchief · 08-31-2007, 03:37 PM

The engines keep getting bigger and have more power. However that comes with a price in MPG.
You are right about the speed. At 55 I get around 13 but at 70 it drops to 10.

wegriffin · 09-01-2007, 10:58 AM

Not to be bragging too much, but along the Texas/Louisiana coast towing our 307 Monty, I get around 22 mpg with my 2005 Dodge diesel----uh, that's 13 on the highway and 9 in town....

Quote:

quote:Originally posted by H. John Kohl

Ann and I made a trip to NY this week. I intentionally drove the speed limit and no more then 60 on the interstate. Going up I got 11.9 and coming back I got 12.2. Also when pulling the hills I did not run the boost over 20 PSI 28 is max for my set up.
Normally when I am pushing the hills and and towing the speed limit I get about 10.5 to NY and back.
I read a post by Cummins that 55 is the turn over number from rolling resistance to wind resistance. These numbers help make a believer out of me.
Cheers,

rogue · 09-01-2007, 11:13 AM

Wegriffin, would you please calculate my MPG, it going to make me feel a lot better

sreigle · 09-01-2007, 01:20 PM

John, does your Dodge have the 4.10 rear axle? I find similar results to yours but mine seems to do best around 60 to 62 mph. It may be a function of rpm related to the torque/hp curves?

In any case, we're 10 miles short of 12,000 on the truck now with exactly 3,600 towing miles. The worst towing mileage we got was in the first thousand miles on the truck in PA mountains with strong headwinds. We got 8.6. Since then we're running from 10.1 to 11.6 for a full day of towing. Solo seems to be about 15.5 to 17.5 in town with 16 to 16.5 most common. Highway depends on terrain, speed, wind, traffic, and number of small towns. We got 19.3 on a 374 mile one way trip from Kansas City to Sioux Falls, SD. Resetting the trip computer while at a steady 70 mph on cruise on flat interstate for ten miles got 23.0 mpg. The trip computer is high by 1/10 mpg over three tanks when I checked the mpg manually so I rely now on the trip computer. I am very, very pleased with the mileage of this truck. On one trip of about 35 miles at 60 mph, solo, in pretty much ideal conditions and a flat road we got just over 21. We have the 3.73 axle. Also, the six-speed 68RFE transmission has the second overdrive, which makes a difference on mileage.

msmoonsatx · 09-03-2007, 03:19 PM

I have the 5.7L turbo diesel with the 6 speed manual transmission. This last weekend traveling from San Antonio to Dallas and returning, I got over 13 mpg towing. My average speed was between 60 and 65 mph. My truck also has the 4.1 rear end differential. This keeps my rpms between 1800 and 2100. I have found that when I am pulling in hilly conditions, it helps to stay closer to 65 than 60. Going up hill my speed drops off fairly quickly below 60 mph. It also helps to let my speed bleed off going up hill and to let off the gas pedal when going down hill. I realize that each vehicle is different and also the driving habits of the individuals. My DW shifting habits are different from mine and can affect the mpg.

By the way, I have found the trip computer in the truck records my average mpg about 1 to 2 higher than when I manually calculate after filling up.

skypilot · 09-04-2007, 06:37 PM

Mark and Steve: I have an 06 5.9L 3500 DRW with 3.73 and auto; have found during my last trip this past week (2200 miles round trip - all interstates/major highways) that my 'sweet' spot seems to be about 1900 RPM which equates to about 67/68 mph. Truck pulls hills fairly well; seems to get best mpg at about the same. Dropping to 55 mph in Illinois (? spelling) - rpm was so low that the engine was lugging so I downshifted (actually switched it so that OD was off completely) and the mileage sank to the high 8's from low 11s (by the computer). So - being honest -- I boosted back up and ran with the big boys at 65 - 69 mph. By the way this was all pulling my 13.4 tall, 12800 pound 5er. If I average 10 mpg overall, I'm happy!!

skypilot · 09-04-2007, 06:39 PM

Steve: Local Dodge guys are trying to get me to trade to an 07.5 / 08 3500 DRW with the 6 speed auto. With your mileages - I'm impressed. I may just have to see them

. By the way, stopped by Dick Edwards last week early and left a message with Wade to say high from you!

H. John Kohl · 09-07-2007, 06:37 AM

I have the 3.73 rear and six speed manual. I guess we will have to compare gear ratios between the manual and automatic to see the full picture.
Cheers,

Eagle Man · 09-07-2007, 01:40 PM

With my D/A, if I go below about 60 the Allison downshifts from 6th to 5th, so I normally run around 62.

sreigle · 09-07-2007, 04:01 PM

Quote:

quote:Originally posted by skypilot

Steve: Local Dodge guys are trying to get me to trade to an 07.5 / 08 3500 DRW with the 6 speed auto. With your mileages - I'm impressed. I may just have to see them

. By the way, stopped by Dick Edwards last week early and left a message with Wade to say high from you!

Jim Jacobia is the guy to say 'hi' to for me. Also, tell him I referred you and maybe he'll send me something! Don't tell him I bought a Dodge, though. I bought several Ford trucks from him.

Have you driven that Dodge? My only worry is wearing out the rear tires. Rather, burning off the rear tires. It does like to break them loose when taking off from a dead stop when I have to hit it a bit to get out in traffic. Makes me feel 40 years younger.

Mudchief · 09-07-2007, 04:02 PM

Eagle Man, that is why I don't run 60 either. When I run faster it take a steep hill to make it down shift.

sreigle · 09-07-2007, 04:08 PM

Dennis, it's very similar with the Dodge. At 60 with the 3.73 axle it will downshift on moderate hills. At 64 it generally will not. A really steep hill will trigger a downshift, though. We had a 10 percenter in PA on one of the US highways and I had been running 55. That was the speed limit but I couldn't run over that with the curves so stayed at 55. On that 10 percenter it downshifted twice (in cruise and tow/haul) and cleared the hill at 50 mph. I thought that pretty good for towing a 14,620 lb trailer. That 10% hill was only maybe half a mile long, though. I really expected the straight six to slow more than that at highway speeds so was very pleased with the performance. In the first 8,000 miles or so on the truck it slowed down more than after it started breaking in.

clutch · 09-07-2007, 07:38 PM

The Cummins makes a lot of torque from 1400rpm's and up. If you dyno one the torque curve climbs quickly to 1400 and then stays flat to around 2800 and more.

Mudchief · 09-08-2007, 06:25 PM

Steve, I don't think anyone could ask more of a truck then that. My total weight is about 21K and that is why I don't complain about M.P.G. And pulling a 8 to 10% grade with that load a truck has the right to down shift 2 or 3 times when you do not have your speed up.

skypilot · 09-09-2007, 01:07 PM

Steve - Cat's out of the bag already (sorry); Stopped in back when and Jim wasn't in but Wade said he knew you as well; said he'd give the 'howdy' to Jim; asked how you were doing and how the 'truck' was working and that is when I spilled the beans so to speak -- told him I didn't know what happened as I missed the thread (if there was one) but that I'd read you had bought a Dodge Mega cab and were currently using it. His response was 'no problem -- we'll see him again and get him back in a Super Duty!!'.

All: Regardless, I still haven't been able to talk to the Ford tech directly but did speak to one of the service writers who I believe to be very knowledgable: the way he explained it to me is that Ford does inject raw diesel fuel just forward of the DPF; at the same time it adds extra fuel to the exhaust cycle to 'heat up the catalytic converter' so that it causes the diesel to ignite in the DFP burning off the soot to ash. Told him of my belief that there was an igniter plug forward of the DFP because of the 'flaming ford' video -- he said 'no such thing exists -- what I was hearing in that video was a bad injector that was putting too much fuel into the cylinder during the exhaust cycle; too much fuel there plus what was being properly added pre-DPF resulted in the flaming'. So that is the latest that I've heard from Ford types. I've been gone so much the past 4 weeks that I haven't spent any time by the Dodge dealer.

Sorry the take so much time/space. Safe camping to all.

lwcdg · 09-09-2007, 02:07 PM

Quote:

quote:Originally posted by skypilot

All: Regardless, I still haven't been able to talk to the Ford tech directly but did speak to one of the service writers who I believe to be very knowledgable: the way he explained it to me is that Ford does inject raw diesel fuel just forward of the DPF; at the same time it adds extra fuel to the exhaust cycle to 'heat up the catalytic converter' so that it causes the diesel to ignite in the DFP burning off the soot to ash. Told him of my belief that there was an igniter plug forward of the DFP because of the 'flaming ford' video -- he said 'no such thing exists -- what I was hearing in that video was a bad injector that was putting too much fuel into the cylinder during the exhaust cycle; too much fuel there plus what was being properly added pre-DPF resulted in the flaming'. So that is the latest that I've heard from Ford types.

When I started lookig into a new truck Ford, GM, Dodge I went to the parts window of Ford and asked the guy to bring up the "cad" of the new emission crap on the 6.4.

It clearly shows 3 sensors each costing 3 or 400 (can't remember) then an igniter to burn off the soot. This was the first time anyone in the service dept. had even looked at the info. techs have not been trained on it yet. I was not impressed with the engine thus I will be leaving the Ford and moving on to another mfg.
Check with your own parts dept to find the answers for yourself. I believe this to be correct info but if I've misunderstood anything please correct me as only good info is of value.
thanks and hope this helps
chuck
ps and the igniter was 12 or 1400 to replace that is when I thought it wuld be a good time to see all of the other mfgs.

BigAl52 · 09-09-2007, 04:15 PM

I think driving a little slower to obtain better mileage is great. But my truck is like Steve's at around 67 to 68 is where I get the best mileage and performance. So just a reminder if you are on a two lane road as I was recently and you want ot run 55 it sure would be nice if we keep in mind to pull over and let the guy who wants to go a little faster go. On my way back this week from our trip I followed someone from Texas with a fifth wheel in tow doing about 55mph at the most. He was in a 65mph zone and had a line of cars behind him of about 8 or 10. Sure would of been nice if he would of moved over in a pull out spot to let us by. Al

simonsrf · 09-14-2007, 05:05 AM

BigAl52,

You should get up just a little bit earlier in the morning...Was that you on my bumper?

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