Best fuel mileage...let's hear your fuel saving tips!
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Joined: Aug 2004
Posts: 137
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From: Southwestern Oregun
leave a little extra air in the tires when unloaded.
currently 65 psi front, 60 rear.
light pressure with the lead shoe.
let up on the throttle before u need to slow down, (coast). less use of engine brake when empty.
use higher gears when possible.
narrower tires than stock. = less rolling resistance and less traction.
street tires, mostly linear treaded tires.
let the truck slow down on hills and speed up going down.
lower the truck, and streamline the under body.
any other suggestions please post them.
cc
currently 65 psi front, 60 rear.
light pressure with the lead shoe.
let up on the throttle before u need to slow down, (coast). less use of engine brake when empty.
use higher gears when possible.
narrower tires than stock. = less rolling resistance and less traction.
street tires, mostly linear treaded tires.
let the truck slow down on hills and speed up going down.
lower the truck, and streamline the under body.
any other suggestions please post them.
cc
Registered User
Joined: Jul 2006
Posts: 338
Likes: 0
OK...
I just got 20.77 mpg with my 1998 one ton 2wd dually.
My engine is the 12 valve with 5 speed and 4:10 gears.(running empty with the tailgate UP)
I also just returned from a 500 mile trip hauling a 1952 Ford Mainline auto on a flat trailer and I got 18.49 mpg.
anyone out ther getting better mileage with 3:55s?
any gidgets and gadgets that REALLY work?
My truck has the stock muffler on it too.
cmon everyone!!! lets hear YOUR fuel saving tips!
GCSS
I just got 20.77 mpg with my 1998 one ton 2wd dually.
My engine is the 12 valve with 5 speed and 4:10 gears.(running empty with the tailgate UP)
I also just returned from a 500 mile trip hauling a 1952 Ford Mainline auto on a flat trailer and I got 18.49 mpg.
anyone out ther getting better mileage with 3:55s?
any gidgets and gadgets that REALLY work?
My truck has the stock muffler on it too.
cmon everyone!!! lets hear YOUR fuel saving tips!
GCSS
Are you figuring your mileage yourself or are you relying on the mileage estimater on your overhead console? Is your timing advanced? Stock injectors?
Registered User
Joined: Dec 2003
Posts: 14,672
Likes: 9
From: Montana
From www.powerspec.cummins.com where you can input several factors including tire size, tranny and differental ratios, etc
Gearing Recommendations Guidelines
1. Select a gearing combination that will result in an engine speed of between 2100-2400 rpm at the vehicle's intended cruise speed (mph).
2. For maximum fuel economy or for vehicles operating 65 mph or faster, select a gearing combination that will result in an engine speed of approximately 2150 rpm at 65 mph checkpoint.
3. Gearing combinations that produce an engine speed less than 1900 rpm at the vehicle’s intended cruise speed (mph) should be avoided.
4. Note: ISB is not intended for weight over 50,000 lbs.
Here's a another good read- Cummins Secrets of Better Fuel Economy http://www.everytime.cummins.com/eve...Whitepaper.pdf
Gearing Recommendations Guidelines
1. Select a gearing combination that will result in an engine speed of between 2100-2400 rpm at the vehicle's intended cruise speed (mph).
2. For maximum fuel economy or for vehicles operating 65 mph or faster, select a gearing combination that will result in an engine speed of approximately 2150 rpm at 65 mph checkpoint.
3. Gearing combinations that produce an engine speed less than 1900 rpm at the vehicle’s intended cruise speed (mph) should be avoided.
4. Note: ISB is not intended for weight over 50,000 lbs.
Here's a another good read- Cummins Secrets of Better Fuel Economy http://www.everytime.cummins.com/eve...Whitepaper.pdf
Registered User
Joined: Apr 2003
Posts: 6,564
Likes: 6
From: Cummins Technical Center, IN
That's a good read, but I think it's not directly applicable to our trucks. It's optimized for industrial B series, not the Ram as far as I can tell.
If the above info from Cummins were directly applicable to Ram owners, we'd see all the 4.10 geared guys getting better mpg than the 3.54 guys-- which we don't.
The reason Cummins mentions 2150rpm as the "optimum" rpm for mpg is that Cummins assumes heavy use at or near max GVWR (even when you put in the light GVWR on their powerspec options), and they'd far prefer that the engine be operated at higher rpm under higher loads. 2150 is simply the lowest rpm that's acceptable to Cummins for extended max-load usage (which is almost impossible to achieve in a Dodge Truck).
Play with the PowerSpec options and you'll see that you never get it to give you an RPM below 2150-- whether you put in a GVWR of <10K or up to 50K.
The powerspec is almost useless for a B series, especially trying to translate it to a Dodge truck. It's ALWAYS going to tell you the same thing: cruise at 2100-2400rpm, and no less than 1900 rpm for extended use.
According to that Cummins link, every 2nd gen CTD with 3.54 gears is geared too tall from the factory-- even with small stock tires.
jh
If the above info from Cummins were directly applicable to Ram owners, we'd see all the 4.10 geared guys getting better mpg than the 3.54 guys-- which we don't.
The reason Cummins mentions 2150rpm as the "optimum" rpm for mpg is that Cummins assumes heavy use at or near max GVWR (even when you put in the light GVWR on their powerspec options), and they'd far prefer that the engine be operated at higher rpm under higher loads. 2150 is simply the lowest rpm that's acceptable to Cummins for extended max-load usage (which is almost impossible to achieve in a Dodge Truck).
Play with the PowerSpec options and you'll see that you never get it to give you an RPM below 2150-- whether you put in a GVWR of <10K or up to 50K.
The powerspec is almost useless for a B series, especially trying to translate it to a Dodge truck. It's ALWAYS going to tell you the same thing: cruise at 2100-2400rpm, and no less than 1900 rpm for extended use.
According to that Cummins link, every 2nd gen CTD with 3.54 gears is geared too tall from the factory-- even with small stock tires.
jh
Registered User
Joined: Oct 2007
Posts: 1,801
Likes: 1
From: Saskaberia, SK
My last 2 tanks of fuel were 14.9 and 15.2 hand calculated. All city driving, back alleys and stop and go traffic (roto tilling business). For me, the mileage module seems to work, I was getting low 13's without it. On the highway, empty I'm getting 22-23 mpg at 67 mph.
Thread Starter
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Joined: Apr 2005
Posts: 326
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From: Greensburg,Ky
Volumetric Efficiency
I guess what we are talking about is PEAK Volumetric Efficiency.
where is it at what RPM.
Obviously it will vary with different factors...load nwind resistance.etc....etc...
I am wondering about increasing fuel pump pressure and atomizing the fuel better..
I wonder if this is attainable and what can /must one do to attain this???
where is it at what RPM.
Obviously it will vary with different factors...load nwind resistance.etc....etc...
I am wondering about increasing fuel pump pressure and atomizing the fuel better..
I wonder if this is attainable and what can /must one do to attain this???
There is no magic rpm for these engines, the best rpm depends on the load. To look at the two extremes, when there is no load, the best rpm to run is idle. However, at wide open throttle, the most efficient rpm is around torque peak or 1800rpm or so. Everything else falls somewhere in between. A lot of people don't realize that lugging is just as bad if not worse than running high rpm, both for fuel economy and for engine longevity. If you could choose any rpm to drive down the highway at, I would choose 1800 for a 12V.
The biggest factor in the mileage that these trucks get is the wind resistance. The resistance is approximately equal to the square of the velocity so slowing down a little makes a huge difference. As an added benefit, you bring your rpms down a little.
There used to be a lot of threads on the different forums about people wanting to go to larger tires to decrease their rpm and increase fuel economy. Most of these people were finding that even though they were running a better rpm, their mileage went down. The reason for this is that they increased the wind resistance(which is more important than rpm) and they increased the rotational inertia.
Look at http://www.everytime.cummins.com/eve...Whitepaper.pdf for some really good info on fuel economy. You need to keep in mind that this is for much heavier trucks with much larger engines that run lower rpm but the principal is the same.
The biggest factor in the mileage that these trucks get is the wind resistance. The resistance is approximately equal to the square of the velocity so slowing down a little makes a huge difference. As an added benefit, you bring your rpms down a little.
There used to be a lot of threads on the different forums about people wanting to go to larger tires to decrease their rpm and increase fuel economy. Most of these people were finding that even though they were running a better rpm, their mileage went down. The reason for this is that they increased the wind resistance(which is more important than rpm) and they increased the rotational inertia.
Look at http://www.everytime.cummins.com/eve...Whitepaper.pdf for some really good info on fuel economy. You need to keep in mind that this is for much heavier trucks with much larger engines that run lower rpm but the principal is the same.
Thread Starter
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Joined: Apr 2005
Posts: 326
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From: Greensburg,Ky
Administrator
Joined: Nov 2003
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From: League City, TX
Best I ever saw was on a trip from Arkansas to Connecticut. We got 23.8 MPG. Had the family in the truck, and the bed loaded with about 1500 lbs.
Our truck has 3.55's and has a camper shell on it as well.
Our truck has 3.55's and has a camper shell on it as well.
100+
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Joined: Jul 2004
Posts: 785
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From: VA
Remove headache rack & do not run agressive mud tires.
When I built & put on my headache rack/stake holders my mileage dropped by 1 - 2 mpg. Likewise when I put on aggressive mudders I also lost 1 - 2 mpgs. My tires are 315s mounted on H2 rims. When I initially put these on (with the BF Goodrich All terrains) my milage increased by 1 mpg over the stock 265s.
When I built & put on my headache rack/stake holders my mileage dropped by 1 - 2 mpg. Likewise when I put on aggressive mudders I also lost 1 - 2 mpgs. My tires are 315s mounted on H2 rims. When I initially put these on (with the BF Goodrich All terrains) my milage increased by 1 mpg over the stock 265s.
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Joined: Jul 2007
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Got ya beat for sure. Mine gets a solid 12.5MPG. It is a 1T crew cab with 35's, but it is just rediculous. It is an older industrial engine and I am going to try bumping the timing and changing the exhaust housing. I have never heard of anyone getting this bad of mileage. It does not matter how I drive it is 12-12.5mpg city or highway.
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Joined: Feb 2004
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From: Northern Iowa
I ran up to Chicago and back over Memorial day. Did a little city driving up there but otherwise mostly 67 mph, 2050 rpm in 5th, 3.55 rear end. Ran 330 miles on a pump-to-pump fill up, pulled the calculator and found 23.01 mpg.
My biggest modification for fuel mileage: The Driver and his driving habits.
My biggest modification for fuel mileage: The Driver and his driving habits.
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Joined: Aug 2007
Posts: 365
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I am in the middle of figuring my mileage out. I think it's going to work out to be about 17mpg mostly city driving. I think I can get it around 21-22 for the highway... we'll see what the numbers work out to be next time I fuel up. I mainly run 1700-2000 rpm on the highway at 65-70 mph in 4th lockup. I am very conservative on the "go pedal" these days and it makes a difference, especially on take-offs. I dunno if this works but lately I've been driving by my pyro and try to keep the EGT's around 600 under no boost on the highway with the occasional 900* passing spike. The lower the EGT, the less fuel being burned...??