Last post on Aug 27, 2012 at 10:06 AM
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Ford F-250 Super Duty, Dodge Ram Pickup 2500, Chevrolet Silverado 3500, Diesel, Truck
#1 of 133 How to get better fuel economy w/your diesel
May 21, 2005 (6:42 pm)
After talking to hundreds of folks across the country I found that the average diesel owner gets 15-16 mpg.
Also what I have found is the "posted speed limit" has everything to do with mpg.
If someone lives where they hardly drive over 60-65 mph unloaded they will most likely brag that they typically get 19-20 mpg.
Someone who drives 75-80 mph will most likely be getting 14-15.
I have personally taken and compared side by side a "broke-in" 05 Cummins and a 05 Power Stroke.
What I found was at if I maintained a speed of 65 mph I averaged 18 mpg. Once I increased my speed to 75 mpg I averaged 14 mpg. SAME TRUCK... 4 MPG DIFFERENCE.
The Cummins actually dropped less mpg than the Power Stroke with the increased speed and I contribute that to the fact that the Cummins hits it torque band faster at lower rpms.
SO IF YOU WANT TO BRAG ABOUT HIGHER MPG "DRIVE SLOWER!"
(I did however talk to a guy the other day that installed a performance module called the Workhorse and says it increased his 05 PS MPG from 15 to 20. He also said towing a boat he still got 17mpg. He said he bought it at www.888luvdiesel.com)
#2 of 133 Re: How to get better fuel economy w/your diesel [trendom]
Jun 03, 2005 (5:16 am)
I'm new to the group, and have a few questions for everyone. Currently I own a quad cab 2500 4x4 diesel Ram and get an average of 14.2MPG with a highway speed of 72MPH. Can anyone tell me from experience how much better fuel milage is switching to a synthetic motor oil? Also can anyone tell me how much better the fuel milage is when using a cold air intake on hte Cummins engine? These are two options I am considering to try to get my MPG to around 18 without easing my foot on the gas pedal.
#3 of 133 Re: How to get better fuel economy w/your diesel [madeinamerica]
by KCRam@Edmunds HOST
Jun 04, 2005 (4:03 pm)
The Cummins is more affected by gearing than anything like motor oil viscosity. My 96 Ram 3500 4x4 with stock tires and 3.54 axles nailed 24.3 mpg over 270 miles at an almost steady speed of 57 mph. My 05 3500 4x4 with 3.73s and stock tires has no trouble hitting 20 mpg at 55 mph. However, I will lose about 1.5 mpg for every 10 mph over that. If you have the 4.10 axles, it will be even worse.
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#4 of 133 bigger tires
Jul 19, 2005 (2:44 am)
some guy was telling me that desiels do better on a bigger tire. but he said after 35" inch tale tires every thing gos to hell gas, axles, transmission.
#5 of 133 overdrive
Jul 23, 2005 (6:28 pm)
I have researched the aftermarket gear vendor overdrive/underdrive that basically gives the cummins diesel 6 spd transmission 11 gears.
I did this after test driving a 2500 Dodge cummins 6spd today and found it very disheartening to be running at 2500 rpm at 75 mph. The Rep at Dave Smith Motors i Idaho told me about the option and my internet research seems to be pretty positive, makes sense if you got 11 gears like a semit truck your engine runs more efficient and thus better mileage. the add on is 2900.00 per the dealer. Any thoughts? anybody running one presently? I do alot of highway driving, rarely tow and want the engine to be relaxed going downt he interstate.
#7 of 133 Re: overdrive [cornfed]
Aug 04, 2005 (4:33 pm)
Gearing is all important with a diesel engine, that's why big trucks have multiple gears. The ones I've had any experience with had 9 speed Eatons, shift 1-5 in low range, then hit high range and go back to 2nd to get 6th gear, then on up to 9th. Unless you can switch the range on that overdrive unit while underway, you'll still only have 6 gears. I admit, I haven't looked at the Gear Vendor unit in a fairly long time, maybe they changed that.
Do you have a 4.10/4.11 gear ratio? 2,500 rpm sounds about right for 75 mph with that ratio. I had an F-350 with 3.73's in it and it ran around 2,100 rpms at 75 mph. I'm afraid that if you go with an overdrive unit, your highway performance will suffer. Turbocharbed diesels need some rpms to get the turbo spinning fast enough to create boost, which in turn builds HP. Find out the overdrive ratio, is it a 15%, 20%, etc... Reduce your engine rpms by that percentage to figure out what your engine speed will be at a given speed in 6th gear. Then get out on the road and try driving in 6th gear with the engine near that rpm. You'll probably want to do this on a not so busy road since you'll probably be driving slowly. Then roll into the throttle. If the truck has plenty of "get-up-and-go" to it, then the overdrive may be an option. I'm betting the engine won't be spinning fast enough. I know how my F-350 drove at 1,600 rpm in 6th gear, even with a chip.
Another option is to just regear your axle. I think that would be considerably cheaper.
#8 of 133 Prince of darkness upgrade injectors
Aug 05, 2005 (2:56 pm)
Has anyone installed the Bosch Upgrade injectors? I have a 12 valve cummins and was wondering if they noticed a difference in their mph or torque and horsepower?
here's a reference link: the exact ones I bought:
auction from the guy I bought from
#9 of 133 ...man sez "drive...
Aug 14, 2005 (12:55 pm)
..I couldn't agree more.
..doing 55 mph (absorbing big time nasty looks from many citizens), my diesel will turn in that same figure in mpg. Increase to average citizen speed and fuel efficiency heads for the cellar.
..so I plan ahead, drive 55 and try to avoid eye contact.......
all the best, ez
#10 of 133 Re: ...man sez "drive... [ezshift5]
by KCRam@Edmunds HOST
Aug 16, 2005 (5:28 am)
Same here... at 55mph, I get a solid 20 mpg in my 05 Ram 3500 Quad Cab 4x4 dually (Cummins, automatic, 3.73 axles). At 65, that drops to about 18.
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