Declining diesel mileage

[Feb14bgirl]

Hi. I just love my 2022 Jeep diesel. That being said, my mileage seems to be declining. On the first trip home from the dealership (about 200 miles) I got 26.9 mpg. I had hoped for 30 (haha) but my husband was in disbelief that I got so good. When I got home I lowered the tire pressure from 38 to 34. The next tank I got 25.5 on the highway. Was averaging 22-23 in town. I got about 25 on the highway for the next tank also but the fourth full highway miles was 24ish. This last highway trip I got 22 on the way there and checked it on the way back and got 23.5. The def is in the 60% full range. I have done no modifications. My driving remains the same. I admit though I do like to be one of the fastest on the road. I guess I expected the mileage to get better over time or at least remain close to the same. NOT go down. Anyone else have this happen or can explain why this is happening and if there is anything I can do? I also a couple weeks ago had the fan come on at a weird time and stay on until I pulled over and shut the Jeep off. It did it one more time then hasn't done it since. I'm describing as a fan noise since I assume that is what it is and it is LOUD! I'm a new Jeep owner so I have no experience with them or diesels. My husband tends to think I hear unnecessary noises but I don't. He took my Jeep to work today and thinks it sounds the same. Help!

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[Santana74]

I have a 23 ecodiesel I bought the end of Oct. I get average 25-26 mpg when driving in town and about 27-28 mpg when I drive in town and some long distance. I've seen 31 mpg on a 50 mile trip on a 2 lane hwy one way. No real elevation differences where I drive normally.

 

[Dailydrivenwrangler]

Where do you live? If you’re in the northern part of the country it’s possible that the diesel your using is now a winter blend which will give you worse mileage.

 

[Paluss]

There are a lot of variables involved in mileage estimates. up hill vs down hill, wind, driver input heavy vs light foot, what speed you drive at, etc. I have just over 4,000k miles on my Diesel and the mileage is about the same as new (although the motor seems to be smoother/broken in now) I am right at half a tank on DEF, I average about 27-29 on highway (65-70mph) and combined 25.6. My mileage has been consistent except for when a regen happens and I have seen the MPGs dropped as low as 20.

 

[Feb14bgirl]

Thanks everyone for your replies. I expected your gas mileage. I live in Texas so it is pretty flat and mostly warm/hot so cold is not an option. Would increasing the tire pressure help much? What are you driving your Jeep at?

 

[Feb14bgirl]

Also, are your mileages what you see on your dash or actually calculated at the pump. I SEE better mileage on the dash than I actually calculate at the pump.

 

[Wbino]

You're driving a JEEP put black electrical tape over the MPG indicator.

 

[Jeff]

I have 2020 diesel with 25000 miles and my milage is 20-25 mpg around town and a little better in the highway. I live on a small island and seldom travel more than a few miles at a time at a slow speed. I have a scangauge to tell me when a regen has started. I drive around in manual at about 2k RPM to keep the temperature up until the regen completes. DEF usage is 1/2 a tank per 5k miles.

 

[BDinTX]

Hey welcome. I think I got in the same ballpark when I drove mine home but almost immediately put on a lift and 35's. With that I've been getting in the mid 23 mph range. The wind around TX can really screw with my fuel economy. I don't hand calculate.

 

[Terpsmandan]

Any wind will decrease you mileage and it does not seem to matter from which direction it's coming.....

 

[BDinTX]

Any wind will decrease you mileage and it does not seem to matter from which direction it's coming.....

Seems like it. I do have a noticeable reduction in cabin noise when I have a tail wind. Most of the time though, when I change direction, the wind flips too so I'm always driving into a headwind.

 

[Paluss]

I run factory settings around 36-37 psi, forgot to mention I have 35 inch KO2s too. Another thing to consider is turbo lag which may cause you to push a bit harder on the pedal, many folks use a throttle enhancer to increase sensitivity. You may want to try one, its an easy install (less than 10 minutes) and they offer 30 day return, so you can compare your mileage for a few weeks...

 

[Terpsmandan]

Seems like it. I do have a noticeable reduction in cabin noise when I have a tail wind. Most of the time though, when I change direction, the wind flips too so I'm always driving into a headwind.

I agree with the tailwind in the rare times it happens....

 

[Feb14bgirl]

You are right about the wind variances. I knew I was driving in heavy wind when I got the 20mpg on the highway. I don't know about the regen and when to expect it to happen. Will I know when it does this and how often does it happen? I have about 7200 miles on my Jeep currently and haven't know if I've experienced one.

 

[Feb14bgirl]

You're driving a JEEP put black electrical tape over the MPG indicator.

Haha

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