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Diesel mileage after break in.

34K views 36 replies 27 participants last post by  Relics 
#1 ·
I've had my XD since September and have always got decent mileage out of it. Usually about 20-21 on the hwy and up till about 2 weeks ago was averaging 18.3 overall. I've read that most people seen an increase in mileage at either the 6000 mile or around 10000 mile mark. I have just hit 12500 and its like you flipped a switch. I have set a new high 3 times in the last 2 weeks and my overall average has went up to 20.2. What really shocked me was that when towing my lawn mower and trailer this week I got 20.4 and in previous tows with the same trailer i had never got more than 16. Maybe my truck is just late to the party but I will take it!
 
#3 ·
I am at 9100 miles on my XD Diesel and I am still waiting for the switch to happen to where I get better than 15 mpg in town. I live in Denver and it seems as though the elevation has some kind of adverse affect on fuel economy but overall the fuel economy in this truck sucks.
 
#31 ·
It's pretty much always been that way concerning engines and altitude. Old carbeurated gas engines and naturally aspirated diesel engines would pretty much "die" at 10,000 feet.
Electronic engines do "correct" somewhat for altitude but air flow is air flow.
A prime athlete whose ran 3.5 minute miles at sea level his whole career will never run a 3.5 minute mile even in El Paso if he hasn't trained there ???.
The old school rule of thumb was that you lost 2.5% engine efficency for every 1000 feet of elevation.
That being said....and I have done it with Cummins ISC and ISL engines, you can use Cummins Insight to program the engine to run at sustained elevations or altitude if the vehicle will be primarily operating it's life there and see some minor gains in efficency. As started though..air is air and if you can't get enough of it you are limited.
 
#7 ·
I'm at 29,000 miles on my Pro4, driving the wheels off of it (bought in Sept). I just saw my truck increase in MPG between 25,000-29,000 miles. On a stretch where I used to get ~20-21 mpg, I'm now getting 23.5 mpg. This is on a flat stretch of road for about 2o miles that I drive about 62 mph (lots of cops), speed limit is 55. I normally drive 80-85 on the freeway (speed limit is 75) and I get 18-19 mpg at those speeds. My avg fuel economy is ~17.5 when I combine in town driving and highway.

I'm strongly considering the AG Diesel module to help with power and slightly better fuel economy. I'd love avg 19-20 mpg with my driving habits:)
 
#9 ·
I have had my 2016 XD Diesel since 10-31-16. As I don't drive the XD extensively, I've only reached 7800 miles yesterday. I have not pulled many loads. I do have the 4WD version. While driving the 278 miles to Houston this week at approx 75-80 mph, I averaged about 17-18 mpg. While driving 70 mph on the return trip, I averaged 23 mpg. So far, I replace 2.5 gal of DEF about every 2800-3100 miles.
 
#10 ·
Diesel Consumption

I have put 3500 miles on my XD Diesel. I really like the vehicle but I am stunned at the shockingly poor consumption.

In the beginning the truck would only get an average of about 9 mpg around town. This was largely due to the fact that the engine wanted to spend lots of time in regen. On some runs it would get up to 19 mpg but that was with super careful driving.

I have made two trips towing an enclosed 20' trailer weighting about 4,000 pounds. My consumption has ranged between 9 mpg and 11.2 mpg. I was hoping for something north of 12 while breaking in.

Yesterday I traveled 200 miles (into the wind) WITHOUT trailer and got 13 mpg all on interstate doing an average of about 70 mph but at times ran it as fast as 81 mph.

Is this to be expected? I have spoken to the dealer and Nissan several times and they want me to wait it out. I just don't know what to think. I can't imagine that the consumption is going to improve by 40-50% after break in. I hear all these stories of people towing and getting 15 mpg but I can't get close. And I would add that my truck used 7.5 gallons of DEF in about 1,200 miles also seems odd.

Any advice will be welcome.
Chris
 
#14 ·
I have put 3500 miles on my XD Diesel. I really like the vehicle but I am stunned at the shockingly poor consumption.

In the beginning the truck would only get an average of about 9 mpg around town. This was largely due to the fact that the engine wanted to spend lots of time in regen. On some runs it would get up to 19 mpg but that was with super careful driving.

I have made two trips towing an enclosed 20' trailer weighting about 4,000 pounds. My consumption has ranged between 9 mpg and 11.2 mpg. I was hoping for something north of 12 while breaking in.

Yesterday I traveled 200 miles (into the wind) WITHOUT trailer and got 13 mpg all on interstate doing an average of about 70 mph but at times ran it as fast as 81 mph.

Is this to be expected? I have spoken to the dealer and Nissan several times and they want me to wait it out. I just don't know what to think. I can't imagine that the consumption is going to improve by 40-50% after break in. I hear all these stories of people towing and getting 15 mpg but I can't get close. And I would add that my truck used 7.5 gallons of DEF in about 1,200 miles also seems odd.

Any advice will be welcome.
Chris
I agree there is an issue. I have 17k on mine; consistent 19-20 highway at 70mph 20-22 at 55mph 15 city and 12-13 pulling my 24 foot 7k camping trailer. 13-15 mpg highway towing my 5k boat which is way more aerodynamic than my trailer.

7.5 gallons of DEF in 1,200 miles is excessive.
 
#11 · (Edited)
That doesn't add up, I get close to 14 mpg city and always 19/20mpg hwy. I just broke 2500 miles and my def gauge just came a little off full, probably as 90%. I haven't added a drop since buying with 21 miles on it.

I pulled about a 26ft 6k trailer and while only about 80 miles total I was probably at or over 12mpg.
 
#22 ·
I don't know how it is possible that your Titan can be so different to mine. I have just hit 6,600 miles and I think i have added at least seven or eight 2.5 gallon jugs of DEF.

In terms of consumption, I once got 20.2 mpg but I was driving so carefully it was ridiculous. Probably better than the test drivers do when they establish consumption figures.

If anything, my consumption has got worse. The dealership was telling me that I would break through this magical ceiling when I hit 5,000. Simply no accurate.
 
#16 ·
It sounds to me like you are stuck in an active regen loop. With such a short drive, it is not able to complete before you are shutting the truck off. So it will start back up the next time you drive after the engine warms up. But if you shut it off again before it completes, the process repeats, and will continue repeating until it completes or throws a MIL requiring you to drive above 55mph for 45 min or more. My suggestion is to add some distance to you commute home to allow the regen to complete. You should notice a definite uptick in mpg to signify that it is done. Then go home.
 
#20 ·
I'm at 14k now. My best mileage is 23.4 and that was doing everything possible to get the best mileage. Reality is, at 70 mph I'm getting about 18 mpg. Towing the boat or trailer at highway speeds I get about 10 mph. Pretty much all driving on flat terrain in Florida.

Like somebody posted earlier, if I wanted better gas mileage I'd have bought a Prius....

I hate a fucking Prius!
 
#23 ·
2016 Pro4x diesel 20k best mpg 23 empty. The truck does have a set in period but no drastic change in mpg. Performance wise the last ECM flash to address Dec issue some hose code etc was a good flash for me. Tires at 65 bone cold 10w30 synthetic blend or 5w40 full synthetic currently running T6 Rotilla. City average 15 highway average 20 combined average 17.1 to 17.6. Burn cycles every 600 to 650 miles for about 20 miles with 11 mpg. Top off DEC set reminder to 2500 and when it pops up add 2.5 gal. Want better mpg? Buy the ecodiesel or baby duramax and tow and hula less. All the new diesels have this smog crap the suck. This is a purpose built truck and does what it's designed to do with flying colors pulse it's comfortable as all **** and fun to drive. For a first year production run it has had some quirks and issues but nothing that one or the other local dealers has not been willing to address. Me like my Frankentruck.
 
#24 ·
I'm getting 14-15 in town. Best I have seen hiway is 17.8. Most of the time I am seeing right at 17 but that is running 75-78 mph. I regen around 12-15 miles @ 8mpg typically. This engine would have been great 15 years ago before all the emissions kicked in. I do miss my 7.3, emission free, didn't even have a cat on it.
 
#32 ·
I am having similar issues. Typical in town driving I only get 12-14 mpg. On the highway driving from Houston to Dallas or Houston to San Antonio running between 80-85 I get 11-13 if I slow down between 70-75 I get round 15. I pulled a 32" travel trailer to Dallas at 75mph and averaged 8-9. I am running 33x12.5x20 tires, 4wd, with about 58,000 miles.

I have recently had 2 instances where my mpg on the computer has dropped to below 5 mpg. I can smell exhaust when I stop at a light. Sending it to the shop to see what is going on.
 
#34 ·
I'm d3l3ted and get about 15-16 mpg at 75 mph. D3l3ting my truck made no difference in fuel economy. I have a leleving kit and slightly larger tires (275/65/20 vs 265/60/20). Bone stock with no leveling kit and stock tires I was still only getting about 17-18mpg on the highway. By comparison my F350 work truck loaded with all kinds if heavy equipment in it does about the same, that's with a bigger engine and way more weight. I think it's the 3.91 rear end that's killing our fuel economy though. I didn't buy it for fuel economy but it would be nice to at least be able to get the same mileage as a 1 ton pickup. And I hate the Prius too!
 
#36 ·
If I really really try I can eek out about 23-24 on the highway but that's parking it behind a tractor trailer. More real-world it's about 20 on the highway.

Around town I try not to drive it because it'll go into regen every 150 miles and I'll end up averaging about 14mpg. My thoughts on the whole emissions mess have certainly been evolving over time. The engineer in me can't believe that what we have is the only solution they could come up with.
 
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