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Posted this on a previous thread, but wanted to get a new discussion going and see if I could get some new/additional feedback from all you much more knowledgeable folk out there. I used this forum as a reference when I was looking up information on my search for a truck, but just joined to post my dilemma after finally purchasing the truck.

I just bought a 2016 Limited with 88,000 miles a 6'4" bed, ramboxes, air suspension, 3.55 ratio and aftermarket rims and tires (still 20" I believe, but slightly over-sized tires at 56lbs per tire). I live in Michigan and purchased the truck in South Dakota. We drove it back (about 772 miles) and on the final fill up we reset the trip odometer. The computer read 503 miles traveled when I filled up and I put 23.7 gallons in it (21.2 mpg). Out of that 503 miles, 420+ miles or so of those miles were highway miles cruising between 73-75mph, I expected it to be much higher. I did not GPS track the actual millage so everything was based on the trip computer (which was a mistake), though I can tell from the zip on my credit card statement that an actual 420 miles were driven on the highway from the fill up. The computer did read an average of 22.3mpg after just the highway mileage home.

I was thinking that I would be at at least 25+mpg for this tank and then my typical driving would drop it to the 22-23mpg range, based on my preliminary research. I am a little concerned because I purchased this truck specifically for the fuel efficiency. I know it is really early so I will keep tracking, but wanted to get it out there and see if anyone could direct me to what I could look into.

I do want to get the GDE tune at some point, but I have the Mopar Max Coverage Warranty transferred to me for 2 more years, so I don't want to void that.

Any ideas? I am not overly mechanically inclined, but I want to do whatever is needed to get it up within reason or I could use the extended warranty to get it checked out but I would love to give them some direction.

I was told there were two open recalls that needed to be completed before the truck could be sold, which was on 7/10, so I believe all the recalls have been completed on the truck now since they were "no sale recalls" for the dealership.

87033
 

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This particular forum is specific to the 5th gen RAM (2019+) with the 3rd gen EcoDiesel engine (again 2019+). Yours is a 4th gen Ram with a 2nd gen Ecodiesel engine, so you may want to repost here: RAM 1500 Diesel General Discussion

FWIW - the recalls probably caused the drop in mileage. Get ahold of GDE and learn more...it is VERY unlikely it will cause any lapse in warranty. That is step one...for sure.
 

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This particular forum is specific to the 5th gen RAM (2019+) with the 3rd gen EcoDiesel engine (again 2019+). Yours is a 4th gen Ram with a 2nd gen Ecodiesel engine, so you may want to repost here: RAM 1500 Diesel General Discussion
When you see a post that is out of place, instead of tell the person to repost it in another part of the forum, just hit report and a moderator can relocate the thread as I have done with this one.
 

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Welcome to the 21 MPG club!!!! There are a few of us in the club. Doesn't seem to really matter what we do, 21 is our magic number. I'm GDE engine and transmission tuned. Didn't do a bit for the MPG and still have more turbo lag than I think I should have (on an original GDE tune). Been to the dealer a few times. They say nothing is wrong.

Cry for a minute, then enjoy your new truck.
 

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Welcome to the 21 MPG club!!!! There are a few of us in the club. Doesn't seem to really matter what we do, 21 is our magic number. I'm GDE engine and transmission tuned. Didn't do a bit for the MPG and still have more turbo lag than I think I should have (on an original GDE tune). Been to the dealer a few times. They say nothing is wrong.

Cry for a minute, then enjoy your new truck.
Dang, I was hoping that wasn't the response I was going to get! ha

I will definitely enjoy it one way or another and love the truck, I am just disappointed in the real fuel numbers that I am seeing, especially when comparing to many of the other forum member's posts.

I did talk with GDE today and they said their new tune is the way to go compared with grabbing one of their old tuned ECU's off the forum. I am just not loving the idea of throwing down another $1,100+ dollars on the truck, when I just spent so much to get the truck I wanted in the first place (yes, I am dutch). I did talk to the dealer that will work with the Mopar coverage and they said if I brought in data from 5 tanks, they will take a look at it and try and assess if anything is wrong. Not holding my breath, but figured since I have the warranty, I mine as well give it a shot.

The guy who traded it in could have made some small modifications to it, no idea.
 

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Check your tire size via the door, factory 20" are 275/60/20 if the tire are different size that could account for part of the fuel economy. Factory 17" are 265/70/17, if you have any else but maybe 285/70/17 the fuel economy and speedo will be off. The 285/70/17 is the factory Rebel tires size and is within 1% of the 20"s
Depending on the weather or how much wind your driving in, that can effect the fuel economy, these trucks have the aerodynamics of a cinder block when it comes to wind.
I was driving down the highway into the wind and the instant fuel economy would barely go over 19, on the return trip less than a half hour later when I was going with the wind the instant read out was 30-32 and I was traveling the same speed as before.
If you really want to squeak the fuel economy out, drive 55-60 mph, you be pushing 30 mpg no problem.
 

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Discussion Starter #7
They are the 275/60/20's - BFGOODRICH ALL TERRAIN T/A KO2.

Thanks for the feedback. I will just track the next 5 tanks and see if it gets any better and hope for the best. May just be a condition thing as you noted.

@UNSTUCK doesn't make me want to go out and purchase the GDE tune as much if he has both the engine and tranny tune and it hasn't done crap for his MPG.
 

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Bronk,
I also have a 2016 Limited. There are a lot of small things that can add up. I did a search for mpg of your current tires, and three different forums all had posts about a loss of .5 to 2mpg, but "it's worth it" they said. You have the longer box that adds just a little weight, you have the Ram boxes that might add a little weight, and I think I can see a tonneau that adds up to 100 pounds. Same with the step bars.
What psi did you have in the tires? Be sure to have at least 40psi for good mileage. The truck really gets better mileage at 70 and under, so that's another minor factor.
Finally, how do you know it's the 3.55 axle ratio? Unless you've seen a copy of the window sticker (which you can get from a Ram site) you can't be sure you don't have the 3.92, which would cost you a little mpg, too. Stock was the 3.55 and the 3.92 cost a little extra, but was often ordered. You could report your RPMs at a given speed, like 60 or 70 and the pro's on this forum could tell you which axle ratio you have.
The first thing I'd do is ask you local dealer to print out a service history, and especially a list of recalls and updates that have been done to your truck.
Bill
 

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When you see a post that is out of place, instead of tell the person to repost it in another part of the forum, just hit report and a moderator can relocate the thread as I have done with this one.
I did not know that was the preferred route...good to know! I just wanted the new member to know there was a difference...good intentions (y)
 

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Discussion Starter #10
Bill,
Thanks so much for the insight and feedback. The tires are brand spanking new from when I bought it, and seem to be fairly highly regarded (and I live in MI, so lots of snow), so I will run them at this point even though I am sure it cost me a few MPG. I totally understand that some of the options I was looking for were going to potentially add some weight/effect the MPG. I do have a roll up tonneau cover, you are correct. I believe the psi for each tire, according to the system, is about 42-43 psi, I will double check that, but I appreciate that direction!
I do have the window sticker, so I am sure it is the 3.55 axle ratio. As I noted, I plan on bringing it into my local dealer after I get the 5 tanks of data to see if they have any feedback (mine as well because I have a max $200 deductible), when I bring it in I will ask for a print out of the service records, but I believe there have been 4 recalls done up to this point.
Have you done the GDE tune @wsonnenb ?
Bronk
 

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You could report your RPMs at a given speed, like 60 or 70 and the pro's on this forum could tell you which axle ratio you have.
With his tire size(275/60/20) at 70 mph in 8th gear:
3.55 gearing: 1700 rpms
3.92 gearing: 1880 rpms
At 60 mph in 8th gear:
3.55 gearing: 1460 rpms
3.92 gearing: 1600 rpms
 

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I did not know that was the preferred route...good to know!
You can even report yourself if you catch the mistake. Sometimes merging makes a mess of combining two identical posts, just moving a post keeps everything in order.
:D
 

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Tuned 2015 crew cab 4x4 short bed 3.55 gears. I can almost get 30 traveling 70 mph in relatively flat terrain hwy trips and no head wind. Change it to 75 mph and even a slow head wind and some hills and the figure changes quite a bit.

Cruise control wont get you your best mileage. There is a good chance you completed a regen in there somewhere if the truck has been sitting on a dealer lot and has been stacking up a few short trips for a while. Driving habits effect fuel mileage dang near more than anything.
 

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Bronk,
I've been seriously considering the GDE tune, but not getting it yet until I decide how long I'll keep mine. The 5-year powertrain warranty runs out in November, with only 59,000 miles, mostly towing a 4200 lb camper trailer. Towing mileage ranges from 20mpg going 55 on back roads to 17 on assorted highways going 62. I have a few tanks (always hand calculated) in the high 20s's but rarely run a full tank without towing.
Bill
 

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I did talk with GDE today and they said their new tune is the way to go compared with grabbing one of their old tuned ECU's off the forum.
This is interesting. The guys at GDE must really be working miracles if they can make an EPA happy tune that is better then their original "dirty" tune. Maybe that was the salesmen in them talking.
 

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This is interesting. The guys at GDE must really be working miracles if they can make an EPA happy tune that is better then their original "dirty" tune. Maybe that was the salesmen in them talking.
I think that's what they have to say too. Regarding mpg. I never really saw any improvement w/ the GDE tune, etc. but I have a Four Wheel Camper on full time. The last 2 tanks though my mpg went up about 10%. I'm not sure if it was because of the recalls or just where I was travelling. We're going on a longer trip next week so that will be the real test.
 

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It's your tires... & mixed with wind & those speeds.

Mine is 6'4" bed & 3.92 gears. Pre-GDE, best was 25/26 in summer fuel. Now i'm +26 on highway. When i switched from RSA tires to Deegan 38s, I lost almost 2 MPG. I now run Kumho similar to Michelins highway tire. You might think about getting a summer set of rims to run highway tires. Not much difference in cost vs new GDE tune. BTW, I wouldn't worry about getting an older used version of GDE ECM. You'll just need to have VIN & injector codes changed (very simple with AlfaOBD & MX connector).
 

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Yup, your tires are the killer; size and weight.

My '17 stock at 65mph would get 31mpg from Ohio to Florida and back. MPG fell pretty quick at 70mph and higher, but I'd still average 27mpg.

When I went from the shitty stock tires to the Kenda Klevr R/T's my mileage fell like a rock and I average 22.5mpg. Overall size of tire is factory, but they are heavy.
 

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Tires play into the issue for sure, but that is not "the" issue. My tires are a stockish replacements, but a different brand. Same size highway tire. My mileage didn't change any going from factory stock to these new tires. Guys with oversize mud tires still do better than I do. If I had to guess, I would say I have weird injectors or maybe higher fuel pressure. Truck runs great, just burns more fuel. One guy on here had the same 21 mpg and changed his injectors and the numbers went way up. I think 28 if I remember right.
 
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