Long Road Trip Report

[HSKR R/T]

I disagree. My computer has not been off by more than .35 mpg compared to hand calculations and most of the time it's less than that.

Mine is usually around 1mpg off. And the +/- factor usually leans to the plus side. Only time it's been fairly close is on a long road trip where it was almost all highway miles on flat roads. My last tank, dash read 15.7, hand calculation came out to 14.5. Current tank I'm at 16.9 displayed and will fill up tomorrow probably.

 

[HSKR R/T]

That is awesome, but just for my clarity, it looks like your truck is 2 wheel drive, yes?

I have a Hemi w/eTorque and 3.92 and I have never gotten mileage as high as you reported, ever. I bought my truck new and it has over 71K miles on it now.

But, I could see 2WD giving you a small improvement over my 4WD, and then your truck's onboard computer reporting 1 - 2 MPG more than what you really got. All that put together would bring you pretty well in line with what I would get over the same drive and conditions that you reported.

All of that is why I am working on trading mine for an EcoDiesel (with a 3.21). I know it won't save me much money (at current fuel prices). But, dang! It just irks me to drive a nice, modern truck and still be averaging 14.1 MPG. I guess it's the principle of the thing, for me, as much as anything.

I averaged just over 19mpg last year on a trip from Omaha, NE to Noble, OK and back. That was when I was still stock tires and suspension. But I'm usually around 14-15 mpg driving around home

 

[FLiPMaRC]

Just got back yesterday. NJ to Sudbury, Ontario, Canada. 12 hour drive each way.

 

[StuartV]

I drove 930 miles today. All Interstate. Adaptive Cruise set at 80 or less the whole way. Generally, set at 10 over the speed limit.

Filled up before I left and reset tripmeter and Fuel Economy display.

I did 522 miles before my first stop. Onboard computer (tripmeter and Econ display both) said 19.8mpg. Hand calculation said 18.0.

Also, remaining range said 55 miles. Truck took 29.022 gallons.

I put the stock wheels and tires back on yesterday. I think that was giving me about 2 MPG better fuel economy than the 32” tires on 20” wheels I’ve been running.

 

[Idahoktm]

I drove 930 miles today. All Interstate. Adaptive Cruise set at 80 or less the whole way. Generally, set at 10 over the speed limit.

Filled up before I left and reset tripmeter and Fuel Economy display.

I did 522 miles before my first stop. Onboard computer (tripmeter and Econ display both) said 19.8mpg. Hand calculation said 18.0.

Also, remaining range said 55 miles. Truck took 29.022 gallons.

I put the stock wheels and tires back on yesterday. I think that was giving me about 2 MPG better fuel economy than the 32” tires on 20” wheels I’ve been running.

The stock tires are 32" also. Unless you were running LT tires, the difference in mpg shouldn't be much.

 

[StuartV]

The stock tires are 32" also. Unless you were running LT tires, the difference in mpg shouldn't be much.

I may be misremembering. If the stock tires are 32, then I think I have been running 33s.

 

[Mr. Grumpy]

That is awesome, but just for my clarity, it looks like your truck is 2 wheel drive, yes?

I have a Hemi w/eTorque and 3.92 and I have never gotten mileage as high as you reported, ever. I bought my truck new and it has over 71K miles on it now.

But, I could see 2WD giving you a small improvement over my 4WD, and then your truck's onboard computer reporting 1 - 2 MPG more than what you really got. All that put together would bring you pretty well in line with what I would get over the same drive and conditions that you reported.

All of that is why I am working on trading mine for an EcoDiesel (with a 3.21). I know it won't save me much money (at current fuel prices). But, dang! It just irks me to drive a nice, modern truck and still be averaging 14.1 MPG. I guess it's the principle of the thing, for me, as much as anything.

This is exactly the reason why I got rid of my 21 Limited with 3.92 gears, I was getting 14.5 MPGs (according to Fuelly) of mixed driving (70% HWY). I ordered an EcoDiesel with 3.21 gears for fuel economy since I don't tow.

 

[834k3r]

I averaged just over 19mpg last year on a trip from Omaha, NE to Noble, OK and back. That was when I was still stock tires and suspension. But I'm usually around 14-15 mpg driving around home

That matches my experience.

 

[StuartV]

Traded for a 21 ED with 3.21, with 17K miles on it, this morning and drove home. 930 miles with adaptive cruise set 10 over. Got 25.5 (calculated by Fuelly). Both times I filled up, the onboard was high. 1.4 mpg high one time and 2.3 mpg high the next time.

 

[HSKR R/T]

Just filled up tonight. Had quite a bit of highway miles on this tank, more than normal. Displayed fuel mileage on dash. 17.1mpg. actual calculated mileage was 16.1mpg

 

[omegafiler]

I recently took a 2500+ mile trip through TX, NM, CO, KS, OK, and the final average was 15.9, per the trip computer. This is a 4WD Limited with 3.21 gears, 22's, at least 89 octane, no towing, one passenger + luggage. Also worth noting, the trip started during the break-in period, there was plenty of 2-lane passing, idling, 40 to 100+ degrees F, some heavy rain, and mountain driving. Given the range of speed limits in each city/state, this could have been anywhere from 55 to 80mph+. So I suppose you could call this a "worst-case scenario," but it isn't too far off from many of my trips. Certainly lots of variety!

If you're cruising under 60, I could totally see getting over 20mpg. But at 70+, that's not happening. That's mostly due to the trans frequent downshift when you hit any incline. There just isn't enough power to hold 8th or sometimes even 6/7. So I'm not totally sold on 3.21 gears if your "highway" speeds are on the higher end of the speedo. Flat roads, lower highway speeds, absolutely.

I'd love to see what the RAM could do with the new V6, or perhaps a couple of extra gears, at some point.

Unimpressive fuel economy and power aside, the ride and handling was easily the most comfortable I've had in a long time. Whether long stretches of empty highway or winding mountain roads, it handled it better than some more expensive luxury vehicles I've had. Comfortable seats, decent stereo, useful tech, plenty of room, etc. Overall, great trip.

 

[StuartV]

I recently took a 2500+ mile trip through TX, NM, CO, KS, OK, and the final average was 15.9, per the trip computer. This is a 4WD Limited with 3.21 gears, 22's, at least 89 octane, no towing, one passenger + luggage. Also worth noting, the trip started during the break-in period, there was plenty of 2-lane passing, idling, 40 to 100+ degrees F, some heavy rain, and mountain driving. Given the range of speed limits in each city/state, this could have been anywhere from 55 to 80mph+. So I suppose you could call this a "worst-case scenario," but it isn't too far off from many of my trips. Certainly lots of variety!

If you're cruising under 60, I could totally see getting over 20mpg. But at 70+, that's not happening. That's mostly due to the trans frequent downshift when you hit any incline. There just isn't enough power to hold 8th or sometimes even 6/7. So I'm not totally sold on 3.21 gears if your "highway" speeds are on the higher end of the speedo. Flat roads, lower highway speeds, absolutely.

I'd love to see what the RAM could do with the new V6, or perhaps a couple of extra gears, at some point.

Unimpressive fuel economy and power aside, the ride and handling was easily the most comfortable I've had in a long time. Whether long stretches of empty highway or winding mountain roads, it handled it better than some more expensive luxury vehicles I've had. Comfortable seats, decent stereo, useful tech, plenty of room, etc. Overall, great trip.

At 80 MPH with 3.21 gearing, on a flat road, you'll be at ~1800 RPMs in 8th gear.

If you had a 3.92 rear end, you'd be at ~2200 RPMs in 8th gear.

So, for highway driving on the higher end of the speedo, yes, if you just tip into the throttle to accelerate gently, the 3.92 will result in a bit better response because it doesn't need to downshift. With a 3.21, it would downshift to 7th first, to get the same acceleration as the 3.92 would have without accelerating.

However, that is a pretty specific, narrow window. I only ever had 3.92 gears until I got an ED with 3.21 this week. The VAST majority of the time, if I was going 80 and wanted to accelerate, I gave it enough pedal to cause even the 3.92 to downshift. And once it downshifts, I think it doesn't matter. The 3.92 might downshift to 7th, and the 3.21 would downshift to 6th. Or 6th and 5th respectively. Regardless, if they both downshift, then neither one is really giving an advantage.

The 3.92 is only an advantage at those higher speeds if you are just trying to accelerate without downshifting at all - and in my experience, that was rare. My 3.92 (with e-Torque to help!) at 80 would still downshift on just about any upslope - even very gentle ones.

At lower speeds, the 3.92 is still tall enough gearing to let the tranny be in a gear that yields "optimal" RPMs. At that point, the truck will run at the same RPM, regardless of which rear end it has, so it will have the same acceleration on tap, with either rear end.

 

[Idahoktm]

The 3.92 is only an advantage at those higher speeds if you are just trying to accelerate without downshifting at all - and in my experience, that was rare. My 3.92 (with e-Torque to help!) at 80 would still downshift on just about any upslope - even very gentle ones.

eTorque does nothing for you at 80 mph.

 

[StuartV]

eTorque does nothing for you at 80 mph.

I mentioned it because it is supposed to help if you are going up a slight hill. So, in *theory* should give a little better mileage than non-eTorque even when cruising on the highway at 80.

At least, that was my understanding. I certainly could be wrong.

 

[mikeru82]

I mentioned it because it is supposed to help if you are going up a slight hill. So, in *theory* should give a little better mileage than non-eTorque even when cruising on the highway at 80.

At least, that was my understanding. I certainly could be wrong.

Idahoktm is right, etorque does nothing for you at highway speeds. You're mistaken about it helping when going up hill, at speed.

 

[omegafiler]

So, for highway driving on the higher end of the speedo, yes, if you just tip into the throttle to accelerate gently, the 3.92 will result in a bit better response because it doesn't need to downshift. With a 3.21, it would downshift to 7th first, to get the same acceleration as the 3.92 would have without accelerating.

Yeah, I get how the gearing works in trucks - mostly speaking to my experience with said gearing. My issue with frequent downshifting was simply maintaining speed on cruise control. As this was primarily due to speed and terrain, it's a significant factor in regard to user-reported fuel economy. Of course, I don't have a 3.92 to compare, so I couldn't say exactly if/how much it would help the 5.7 in this scenario. I think more low-end torque would do wonders.

Driving on some flat NM roads at annoyingly slow "highway" speeds, it was great MPG (e.g., EPA figures), as it happily stayed in 8th most of the time. Back to TX, higher speeds, and even smaller hills, forget it. At least it has a 33-gal fuel tank! I love that option.

I suppose most of my last vehicles had a better power-to-weight ratio, so the downshifting of multiple gears was quite noticeable during the trip. As well as the final MPG results.

 

[StuartV]

Yeah, I get how the gearing works in trucks - mostly speaking to my experience with said gearing. My issue with frequent downshifting was simply maintaining speed on cruise control. As this was primarily due to speed and terrain, it's a significant factor in regard to user-reported fuel economy. Of course, I don't have a 3.92 to compare, so I couldn't say exactly if/how much it would help the 5.7 in this scenario. I think more low-end torque would do wonders.

Driving on some flat NM roads at annoyingly slow "highway" speeds, it was great MPG (e.g., EPA figures), as it happily stayed in 8th most of the time. Back to TX, higher speeds, and even smaller hills, forget it. At least it has a 33-gal fuel tank! I love that option.

I suppose most of my last vehicles had a better power-to-weight ratio, so the downshifting of multiple gears was quite noticeable during the trip. As well as the final MPG results.

Right. But, the point is that the downshifting, in and of itself, is not what hurts mileage. It's the higher RPMs that you're turning after it downshifts. So, 3.92 would not help (in my opinion) with mileage at highway speeds. If the 3.21 downshifts, it's going to be running the same RPMs that the 3.92 would.

A big Hellz Yeah on the 33 gallon tank. I drove my Hemi w/3.92 522 miles the other day without stopping. Still showed 55 miles of range left when I finally did stop. I love that. Now I have the EcoDiesel with a 33 gallon tank. I don't see myself ever driving this one from Full to near Empty without stopping, at least to pee...

 

[HSKR R/T]

Right. But, the point is that the downshifting, in and of itself, is not what hurts mileage. It's the higher RPMs that you're turning after it downshifts. So, 3.92 would not help (in my opinion) with mileage at highway speeds. If the 3.21 downshifts, it's going to be running the same RPMs that the 3.92 would.

A big Hellz Yeah on the 33 gallon tank. I drove my Hemi w/3.92 522 miles the other day without stopping. Still showed 55 miles of range left when I finally did stop. I love that. Now I have the EcoDiesel with a 33 gallon tank. I don't see myself ever driving this one from Full to near Empty without stopping, at least to pee...

Actually, shifting up.and down does effect fuel mileage. Might not be something most people would be able to accurately calculate to realize the effect, but there is a negative effect. Everytime the transmission shifts, the torque converter unlocks reducing efficiency. So if the 3.21 geared truck is shifting more often, that's not good