2021 eco diesel gas mileage

[nc_beagle]

FWIW, at any given speed in any given gear (like 65mph in 8th gear) the engine MUST be at a specific rpm. This is purely mathematical, based on the gear ratios. (Any difference should be transitory, based on torque converter lock up and good clutch packs in the transmission.) Consider the engine to be mechanically linked to your tires at a fixed ratio. (That ratio changes only based on your transmission gear selection.)

So, whether or not you're towing or going on the flats or uphill, in 8th gear at 65mph you engine will be at 1750 rpm. (<- example only: the actual numbers may be different. I did not do the maths.)

The difference is how much FUEL it takes to keep the engine at that rpm. In that regard, the Euro/Canadian method of measuring Liters used per Kilometer would give a better idea of exactly how much more work the engine is doing when towing.

Well, I guess I never stopped to think about it, but that does make sense... Thanks!

 

[Aseras]

FWIW, at any given speed in any given gear (like 65mph in 8th gear) the engine MUST be at a specific rpm. This is purely mathematical, based on the gear ratios. (Any difference should be transitory, based on torque converter lock up and good clutch packs in the transmission.) Consider the engine to be mechanically linked to your tires at a fixed ratio. (That ratio changes only based on your transmission gear selection.)

So, whether or not you're towing or going on the flats or uphill, in 8th gear at 65mph you engine will be at 1750 rpm. (<- example only: the actual numbers may be different. I did not do the maths.)

The difference is how much FUEL it takes to keep the engine at that rpm. In that regard, the Euro/Canadian method of measuring Liters used per Kilometer would give a better idea of exactly how much more work the engine is doing when towing.

That's assuming your final drive, and tire sizes are the same. But yes they are related.
Older automatics before torque converters had a lock up used to "overdrive". Lots of excess heat, but more power at certain times.

 

[c3k]

That's assuming your final drive, and tire sizes are the same. But yes they are related.

^^^

Yeah, that's why I emphasized the parts I emphasized and put the other parts in parantheses.

A specific truck will have a specific engine rpm-to-vehicle speed ratio for each gear. That'll be fixed at each rpm for each gear. E.g., 7th gear, 2100rpm=62 mph: or 8th gear, 1750rpm=62mph (<- made up numbers) (And, as I stated, the assumption is that the torque converter is locked up and that the transmission has fully shifted into that gear.)

That's why there's so much debate about tire diameters, final drives, etc. Changing those allows the truck owner to change that engine rpm to vehicle speed ratio.

Older automatics before torque converters had a lock up used to "overdrive". Lots of excess heat, but more power at certain times.

Overdrive did the opposite: it took away power, but gave more speed. It was an extra top gear, useful on those old 3 (and four?) speed transmissions. So, instead of driving at 3,000 rpm at 60mph, (because the transmission was geared low in all three speeds so you could get fast acceleration), you could hit the Overdrive button and do that same 60mph in 3rd at 2,500 rpm. (<- as always, I'm making up my numbers for the example.)

Overdrive was sometimes available in more than just the highest gear. It's a cruising feature, meant for those times when you don't need power.

It started out as a physical gear (planetary) behind the transmission, feeding the prop shaft. When engaged, the prop shaft would spin faster than the transmission input shaft (engine crank). It gave a higher than 1:1 gear ratio. Nowadays, with more gear ratios available in our transmissions, the term "overdrive" has morphed to mean any gear with a ratio higher than 1:1. Meaning, if the engine is rotating slower than the transmission output shaft, it'll be called an "overdrive" gear. These are your cruising gears.

(For clarity, "Underdrive" means the transmission output shafts spins at a speed "under" the input shaft speed. For example, in 1st gear, the engine crank/transmission input may spin 3.5 times for each 1 time the output shaft spins. It's "under driven".)

Here's a good link: What Is Overdrive Transmission And How It Works? - Engineering Choice

 

[c3k]

Look at my sig for specifics... 3.21 Final Drive and 33" tires.

In 8th gear, 1500 rpm, 68 mph. (Both speedometer and GPS)
In 8th gear, 1750 rpm, 78 mph. (Both speedometer and GPS)

 

[TonyCA]

Look at my sig for specifics... 3.21 Final Drive and 33" tires.

In 8th gear, 1500 rpm, 68 mph. (Both speedometer and GPS)
In 8th gear, 1750 rpm, 78 mph. (Both speedometer and GPS)

Seems about right and just rounding errors?

Using this calculator: Calculate RPM for Given Speed(MPH), Rear Gear Ratio, and Trans Gear Ratio
Assuming a 0.67 8th gear ratio per RAM: https://s3.amazonaws.com/chryslerme...022_RAM_1500_SPljhbq4p17a2llk0gffhcnq6vp6.pdf

68 mph w/33" tires a 3.21 final drive and 0.67 gear ratio gives 1489.07 RPM
78 mph w/33" tires a 3.21 final drive and 0.67 gear ratio gives 1708.05 RPM

 

[KirkG]

On my way home from picking up my Laramie 4x4 Ecodiesel(3.21 rear), driving from Idaho to Pa via Yellowstone and dealing with a big spring winter storm. Mostly driving at 75 on cruise control but a really healthy tailwind lol

 

[BNJMN]

View attachment 127609
On my way home from picking up my Laramie 4x4 Ecodiesel(3.21 rear), driving from Idaho to Pa via Yellowstone and dealing with a big spring winter storm. Mostly driving at 75 on cruise control but a really healthy tailwind lol

With that much range showing isn’t this only a couple of miles driven that achieved this mpg?

 

[nc_beagle]

With that much range showing isn’t this only a couple of miles driven that achieved this mpg?

Or, he just refilled?

 

[KirkG]

I had driven from Nampa ID to Yellowstone and had just refilled in Gardiner MT when I took that picture. Sitting in South Bend IN now and am still at 31 mpg… seriously I have only filled up once since leaving Yesterday and due to winter storms have driven around Wyoming!

 

[BNJMN]

I had driven from Nampa ID to Yellowstone and had just refilled in Gardiner MT when I took that picture. Sitting in South Bend IN now and am still at 31 mpg

That’s amazing! Will be interesting to see how it moderates over time. I averaged 22 my first tank. Now closer to 23 on my second but I haven’t had my trailer on yet this tank.

 

[KirkG]

That’s amazing! Will be interesting to see how it moderates over time. I averaged 22 my first tank. Now closer to 23 on my second but I haven’t had my trailer on yet this tank.

Keep in mind that was with a healthy tail wind and driving slowly in Yellowstone but I am really loving this truck and with the 33g tank it’s amazing how far I can drive. I really will make it from Gardiner Mt to Lancaster Pa on 2 tanks of fuel

 

[KirkG]

 

[bucolic]

I hit my best mileage ever on a trip from Atlantic City to Upstate NY a total of 249 miles. It took 4hr 9min so it was an average speed of about 62 MPH.

I was doing the speed limit which was probably about 70 MPH half the trip on the PA Turnpike and 65 the rest with the occasional 55 MPH stretches.

It seems to have gotten better as the truck has acquired some miles. I have 3.21 gears and the options that add weight like Ram Boxes, Sunroof, and Multifunction tailgate so it's probably one of the least fuel-efficient setups as far as options go.

I am pretty impressed with this for such a heavy vehicle.

Now if we can just get diesel back down to the $4.00 a gallon mark instead of $5.29

 

[Malodave]

I am averaging 24.7 on my 30 mile commute with winter blend. Some Hwy but mostly small towns.
I have the GDE Trans Tune installed too. 26K Miles on the Truck.

Malodave

 

[wiskyram]

After a little over 1 year (purchased 3/17/21) and 36000 miles my fuelly average is right at 27 mpg. Mostly back highway for commute. Will have a longer trip coming up in a week. It was higher before the winter blend, cold Temps and much more idle time. Pretty happy with that. Not happy with $5 per gallon but whatever. Still would be spending more with my old gas truck

 

[monkeypunch]

4k miles in and getting 23mpg, maybe a hair less. My truck is a pig.

 

[AV8OR]

I’ve done two long haul 800 mile trips (no trailer) since I took delivery of my truck in February.

The rest of the mileage has been city driving.

I’ve never reset Trip B since I took delivery so I can keep a running mileage.

My milage is nothing close to what Ram said I should be getting even with the 3.21 rear end…..and yes I crawled under the truck to make sure Ram put in what I ordered.

 

[AV8OR]

I dragged raced it today 0 - 60 mph -

 

[tom318]

I'm impressed yet again with this engine. Just wrapped up a nearly 900mile round trip towing ~5500#s and averaged 17.5mpg on the first half and 18.5mpg on the return home. averages are based on hand calculated and not from digital gauge. Driving relatively slow @ mostly 65-68mph. By myself in the truck with minimal gear in the truck. Truck mostly stayed in 8th with tow/haul on. Image is of the first half.

 

[bucolic]

I'm impressed yet again with this engine. Just wrapped up a nearly 900mile round trip towing ~5500#s and averaged 17.5mpg on the first half and 18.5mpg on the return home. averages are based on hand calculated and not from digital gauge. Driving relatively slow @ mostly 65-68mph. By myself in the truck with minimal gear in the truck. Truck mostly stayed in 8th with tow/haul on. Image is of the first half.

View attachment 130296 View attachment 130297

That's pretty impressive mileage!
I'll be towing a camper that is about 5000 lbs and suspect the wind drag will keep me in the 10-11 MPG range. What you are towing there compared to a camper with that wind sail is a world of difference. That wind resistance is a MPG killer.