This MPG is why I bought the 3.21

ramffml said:

And lets face it, if there was even the slightest possiblity that the 3.92 was more efficient, Ram would not offer the 3.21 at all. Why would they? These guys are now prescribing ditch water instead of 30 weight oil, carefully selected minivan tires, active grills, and increased oil temps, all to save a fraction of an MPG.

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Yet MDS doesn't save a fraction of an MPG? They went through all those other lengths but then spent time and money engineering a system that doesn't?

I suspect you see more people posting mpgs with 3.21 for the same reason you'd see more people posting 0-60 with 3.92s. Self-selection of people who care about those things and purchase decisions.

ramffml said:

Think about my engine revving 400 to 500 rpms lower than yours, for 3 hours... sustained. Going the same distance, same speed, same tail wind, same fuel, yet you're revving 400+ rpms over mine. That's why the 3.21 is going to get me much better mpg.

It's like you can only think in terms of "prius" or "mac truck" and nothing in between. I bought my truck to pull my trailer. So I "need" the truck. Those times when I'm not pulling, I'm definitely concerned about MPG.

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No way a hemi is going to cruise at 28 mpg regardless of the rear end . Of course maybe if you hand calculated with that new common core math I hear about. But I use the old miles divided by gallons used.

Wild one said:

There's a theory floating around,that the trucks actual exhaust system,might be a bigger contributor to manifold bolt breakage,then we think.Example being the 5.7 cars use basically the same cast iron log manifold,but with a set of dual pipes,that lead back to an X farther towards the rear of the car,then the trucks squashed midpipe is,and the cars don't break manifold bolts. The theory does make you wonder if the actual exhaust system on the trucks might be putting more stress on the back manifold bolts,then we think,as it's always the back bolts that break,which is where the exhaust pipes would be exerting the most pressure.You'd think if it was totally heat related and temp changes breaking bolts,the front bolts and middle bolts would be more inclined to break,but i've never seen or heard of a truck actually breaking a front manifold bolt

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First, you know more than I do.

IMHO, like the failing lifters and camshaft, There is never any one reason for the failure. Been my experience things like this always have multiple causes.

Docwagon1776 said:

Yet MDS doesn't save a fraction of an MPG? They went through all those other lengths but then spent time and money engineering a system that doesn't?

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I didn't say it didn't save a fraction. I literally said my gut feeling is that it should save some. But yes, they went through a lot of trouble to put out MDS, so if there was any chance whatsoever that the 3.92 would save money over the 3.21 then they would simply not offer the 3.21.

Docwagon1776 said:

I suspect you see more people posting mpgs with 3.21 for the same reason you'd see more people posting 0-60 with 3.92s. Self-selection of people who care about those things and purchase decisions.

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I suspect the opposite; all you guys with the 3.92 that refuse to accept your reduction in MPG would be trying to prove how superior their 3.92 is, "look, it's even better on gas!!!".

I like discussions but some of you all truly got blinders on.

huntergreen said:

No way a hemi is going to cruise at 28 mpg regardless of the rear end . Of course maybe if you hand calculated with that new common core math I hear about. But I use the old miles divided by gallons used.

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I don't know what common core math is, unfortunately. No doubt the computer is optimisitic, the point is the 3.21 is dominating the reports of high MPG.

ramffml said:

Couldn't resist after seeing a bunch of negative posts on the 3.21. I get why this forum is so lopsided, it's an enthusiast forum so many will be drawn to the 3.92.

But this week I just crushed my best record to date (which was 2 years ago). Back then the best I got was 9.4 l/100 km = 25 mpg. This week, my truck displayed this little goody on the dash:

8.4 = 28 mpg

3 hours 100% freeway driving, avg of 103 km/h, with a light tail wind, MDS disabled, mix of 89 and 91 octane fuel, probably some ethanol in there but cant be certain of the amount.

Reset meter, hopped on the freeway, and snapped pic after 3 hours on the off ramp. So yes, all ideal conditions but it's still far better than anything I've seen with the 3.92. And I probably won't see that again ever, but there is no doubt the MPG savings of the 3.21 are real.

View attachment 497724

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My Eco Diesel just got 30.3 MPG on a recent 330 mile trip to Wisconsin

RF Ram 1500 said:

My Eco Diesel just got 30.3 MPG on a recent 330 mile trip to Wisconsin

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3:21 Rear Axle with 4 Wheel Drive - ‘22

ramffml said:

I don't know what common core math is, unfortunately. No doubt the computer is optimisitic, the point is the 3.21 is dominating the reports of high MPG.

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No doubt the 3:21 will get better mileage. But no way our trucks with 390 hp, 5.7 (345 cubic inches ) are getting 28 mpg even in ideal conditions. There is that thing called physics. For what it’s worth., I have the 3:92. In my world, lots of hills, i actually get better mpg than the 3:21. On the hwy I could top 20 mpg but I just drive normal. And usually top out a bit over 19 on long trips. I’m not biased, as far gear ratio goes. Bought my 16 off the lot, wife picked it out, just happened to have the 3:92. Coming from an 11, if you look at the gearing , the 3:21 with the eight speed exceeds the 3:92 with 5/6 six speed.

Son and I made identical trip two weeks ago. One truck a 2017 RAM Sport Crew cab, 5.7, 3.92 rear, with mds, second truck is 2022 Lone Star quad cab, 5.7, 3.21, with mds. Neither had any load, both have identical bed covers, both had only 87 octane gas from same pump, both have same tires and size 275/55-20 Pathfinder A/T. Trip covered 631 mikes round trip, swapped who was front or rear every 100 miles. Both used cruise control above 25 mph. The 2022 averaged 23.4 mpg, the 2017, averaged 22.7 mpg. The 2022 has 3017.4 miles on it, the 2017 has 42377.6 miles. We also changed driver position at the 100 mile mark. The 2023 is red, the 2017 is orange, maybe the colors weigh different also. They both use same oil, Mobil 1 extended performance, 5W-20. Not much difference between the two really. In fact so close it is pretty much a wash!!!

Oh, the 2017 is a 4X4, the 2022 is a 2WD, both are sure-grip

huntergreen said:

No way a hemi is going to cruise at 28 mpg regardless of the rear end . Of course maybe if you hand calculated with that new common core math I hear about. But I use the old miles divided by gallons used.

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I cruise at 26-27 miles per gallon on my 5.7L consistently.

boblonben said:

Son and I made identical trip two weeks ago. One truck a 2017 RAM Sport Crew cab, 5.7, 3.92 rear, with mds, second truck is 2022 Lone Star quad cab, 5.7, 3.21, with mds. Neither had any load, both have identical bed covers, both had only 87 octane gas from same pump, both have same tires and size 275/55-20 Pathfinder A/T. Trip covered 631 mikes round trip, swapped who was front or rear every 100 miles. Both used cruise control above 25 mph. The 2022 averaged 23.4 mpg, the 2017, averaged 22.7 mpg. The 2022 has 3017.4 miles on it, the 2017 has 42377.6 miles. We also changed driver position at the 100 mile mark. The 2023 is red, the 2017 is orange, maybe the colors weigh different also. They both use same oil, Mobil 1 extended performance, 5W-20. Not much difference between the two really. In fact so close it is pretty much a wash!!!

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Are either truck equipped with the air suspension?

On my Ram 1500, '15 5.7L QC, AT tires, canvas bed cover, Corsa exhaust, 33 gal tank, get just or a bit over 23 MPG on the highway, and as much as 16 MPG local, but rarely as I like driving With the air ride lowering at highway speeds, IMO, also helps a bit with MPG's.

huntergreen said:

In my world, lots of hills, i actually get better mpg than the 3:21.

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The same gear ratios are available in both trucks, except our first and 8ths are different. Which means in the city or anywhere the 3.21 is not in 8th, the trucks will be, for all intents and purposes, equal. When the trucks are on the freeway in final gear is where the 3.21 will get better mpg.

I am sorry and I do not intentionally want to P anyone off but when people buy a truck and complain about MPG sort of hits me wrong. If you want the MPG of a car buy a car.

I am happy for anyone getting good MPG.

If a person likes driving on interstates at 60mph in Texas where most interstates are 75 they need to move over. Take secondary roads. That is what I do if I am not pressed for time, especially on my motorcycle. They are more enjoyable and you get to see Americana.

leroys73 said:

I am sorry and I do not intentionally want to P anyone off but when people buy a truck and complain about MPG sort of hits me wrong. If you want the MPG of a car buy a car.

I am happy for anyone getting good MPG.

If a person likes driving on interstates at 60mph in Texas where most interstates are 75 they need to move over. Take secondary roads. That is what I do if I am not pressed for time, especially on my motorcycle. They are more enjoyable and you get to see Americana.

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LOL, when on IH 35, I have to run 75-85 as U know to keep from getting run over. I got a Big MC, Big Triked Wing, and I stay away from IH 35 with it, not like getting run over. I have the power to run fast, but no enjoyment there. But if I am on IH 35, I am prob heading South towards Austin, and there isn't nothing more disconcerting then running at 80 mph, and down to 10 mph, in a very short period, especially nearing Round Rock, etc.,.

Just FYI, the Trike will run almost 160, but it is governed at 124.9 mph, lol. I can get almost 30 mpg on the Trike, nothing to brag about, lol. Once I get to 80 mph and higher, mpg's go down to like 27.




ADDED: IMHO, very humble, U want high mileage, a Hemi truck or even a ED not gonna get U there, U do need a Prius, lmao.

leroys73 said:

I am sorry and I do not intentionally want to P anyone off but when people buy a truck and complain about MPG

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Nobody here in this thread is complaining about the MPG.

leroys73 said:

If you want the MPG of a car buy a car.

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Cars are capable of pulling my 6000 pound trailer? Gee, I'm sure out of the loop these days.

leroys73 said:

I am happy for anyone getting good MPG.

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You don't sound happy to me.

leroys73 said:

If a person likes driving on interstates at 60mph in Texas where most interstates are 75 they need to move over. Take secondary roads. That is what I do if I am not pressed for time, especially on my motorcycle. They are more enjoyable and you get to see Americana.

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See, you're not happy. In fact now you're the one complaining.

I've always driven at or above the speed limit. Not tested on animals. Your mileage may vary.

I can regulary pull down over 30mpg with the wifes 6.4 Challenger,by slowing down a bit and driving for milege .

crazykid1994 said:

Idk if yours is that way but when I used to get 18-19mpg my computer said 19-20mpg. Now that I get 12-13mpg my computer will say anywhere from 13-15mpg. It’s almost always been 1-1.5mpg off when I had calculate.

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They don't call them a lie-o-meter for nothing.

ramffml said:

Nobody here in this thread is complaining about the MPG.

Cars are capable of pulling my 6000 pound trailer? Gee, I'm sure out of the loop these days.


You don't sound happy to me.



See, you're not happy. In fact now you're the one complaining.

I've always driven at or above the speed limit. Not tested on animals. Your mileage may vary.

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It's 120* and 90% humidity in Texas. Driving the speed limit will allow the engine to run cooler.

I would suggest this thread get split to those who hand calculate (miles/gals) vs. those who take pix of the EVIC after a wind driven, level ground or downhill, perfect weather day with little or no payload! Before anyone gets upset, I'm being somewhat facetious.

Again, most examples (including mine) are anecdotal and unless we're comparing vehicles with only one variable between the two the comparison is flawed. The closest thing I've read in this thread is the example that boblonben posted back on page 5. And then again, in that comparison we're comparing a 2WD to a 4x4. The mpg you get (or think you get) is what it is. If you don't care, that's ok. If you do care good for you!

I just read where idling vehicles waste a horrific amount of fuel every year!


I drives me crazy when both my son and daughter start up their vehicle, adjust the seat, adjust the mirror, adjust the climate, set the entertainment and then think about pulling away. Guess I'm becoming my father!

I'd bet both hand calculated mpg and EVIC mpg would increase if idling was limited. Here is another variable that can affect comparisons between drivers.

I'll stop for now as I'm sure I haven't changed anyone's mind or mileage! Be safe and take care!

P.S. That be safe was absolutely sincere. My best friend's daughter hit a deer the other night with her brand new Chevy Trailblazer. Fender and hood wrinkled, air bags deployed but it was drivable and she was bruised but ok. Accepted insurance estimate was $15000.00+! YIKES!