MPG Steadily dropping….

[DBravo]

I just turned over 11,000 miles about a week ago. I replaced my engine air filter and took the Gladiator in the next day for my 2nd oil change. Ever since, I’ve noticed that my mpg is steadily dropping. I rarely ever get less than 20 mpg in town but I’ve dropped to 17 average over the past week. I certain that my air filter is installed correctly. Tire pressure is sitting at 35 on 37” KO2’s, which is normally the pressure that I run. I have a new fuel filter that I will install this weekend. Has anyone else seen anything like that before? Maybe the fuel filter change will help?

Could it be that it is the declining mpg caused by the larger/heavier tires affecting the "average" mpg? That would depend on if you started with 37's or changed over more recently.

I run stock 255/70/18 GY Wrangler AT on my '20 Gladiator Overland and still average 20 city to 23 hwy after 68,000 miles. I run 35 psi as well. My wife runs Wildpeak AT3w 285/70/R18 on her '21 Sahara and gets between 17 city and 20 hwy. Both have the 6 cyl engine and 8 spd auto.

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[Gren71]

I thought I posted this in the diesel forum.

You definitely did and I didn’t notice that haha my bad. I saw the thread pup up under the “what’s new” section.

 

[Escape.idiocracy]

Your profile says Minnesota- what have the temps been?? I’m in the PNW and winter diesel doesn’t usually show up until the end of October beginning of November…. You get significantly colder than we do- just never paid any attention to When your temps drop.

I would blame winner fuel…. And maybe also call the dealer and ask if they updated any software while in.

 

[Sandevino]

Hand calculated mpg drop or lie-o-meter drop?

 

[Mike-len]

Your profile says Minnesota- what have the temps been?? I’m in the PNW and winter diesel doesn’t usually show up until the end of October beginning of November…. You get significantly colder than we do- just never paid any attention to When your temps drop.

I would blame winner fuel…. And maybe also call the dealer and ask if they updated any software while in.

I did recently hear on the news that they’re switching over soon, so maybe they already did. And I do remember filling up with diesel the day before I had the oil changed.

 

[Mike-len]

Could it be that it is the declining mpg caused by the larger/heavier tires affecting the "average" mpg? That would depend on if you started with 37's or changed over more recently.

I run stock 255/70/18 GY Wrangler AT on my '20 Gladiator Overland and still average 20 city to 23 hwy after 68,000 miles. I run 35 psi as well. My wife runs Wildpeak AT3w 285/70/R18 on her '21 Sahara and gets between 17 city and 20 hwy. Both have the 6 cyl engine and 8 spd auto.

No it’s definitely not the tires. I’ve had the tires on for at least 6 months. We took a trip out west to Montana, Idaho, and Wyoming, and I was averaging 22-24 (on the gauge) for the total trip of around 2500 miles even through the mountains. It definitely started around the time I had the oil changed, but I also remember filling up with diesel the day before. I think our area has already switched to winter blend diesel, so I think I may have figured it out after someone else here mentioned it.

 

[ZoMojave]

Best I ever got was 17 mpg on 33's in rural summer driving. Wisconsin winter blend dropped it to 14.

Sounds about right.

 

[Mike-len]

Best I ever got was 17 mpg on 33's in rural summer driving. Wisconsin winter blend dropped it to 14.

Sounds about right.

Gas engine? I’m running diesel. And yeah I’m noticing it dropping about 3 mpg lower than normal since I filled up last, so I’m thinking it must be the winter blend.

 

[Volt0]

Also, could you have a battery ( or two ) starting to fail, and working the alternator harder?

 

[HVYMETL]

I thought I posted this in the diesel forum. Stock 3.73 gears. I’ve had the pedal commander since it was new. I’ve been getting 20 mpg on it around town with bumper, winch, Go fast camper, and yes on 37’s. I’ll average 24-25 on the interstate at 65-70 mph loaded with camping gear. It just all of a sudden started dropping. I’ve had the mods on for at least 6 months.

You notice how much more power you have since it's cooling down from summer. I know my diesel is loving it. I definitely think you should be getting 20, but I don't know your driving habits. Cooler temps do bring mpg down as stations are bringing in winter fuel. Just a possibility...

 

[HVYMETL]

Gas engine? I’m running diesel. And yeah I’m noticing it dropping about 3 mpg lower than normal since I filled up last, so I’m thinking it must be the winter blend.

I get 23-24mpg with 35s. I adjusted tazer for my 4.88s and 35s. I run 30psi and drive it hard. Might get better once I get my 38s

 

[Koolcarguy]

I just turned over 11,000 miles about a week ago. I replaced my engine air filter and took the Gladiator in the next day for my 2nd oil change. Ever since, I’ve noticed that my mpg is steadily dropping. I rarely ever get less than 20 mpg in town but I’ve dropped to 17 average over the past week. I certain that my air filter is installed correctly. Tire pressure is sitting at 35 on 37” KO2’s, which is normally the pressure that I run. I have a new fuel filter that I will install this weekend. Has anyone else seen anything like that before? Maybe the fuel filter change will help?

Might be winter fuel? Change the.fuel filter see if that helps. I'm getting 21 to 23 around town hand calculated 25 26 on the highway on 37's after market bumpers, winch and soft topper. I've been getting better mileage as the diesel breaks in. My wife who literally only drives around town very rarely over 55 never on the hwy has a 22 Tuscadero Rubicon unlimited diesel she gets 30 to 31 hand calculated but drives like the grandma she is lol (nobody tell her I said that) I change oil at 7500 miles and air/fuel filter same time rotation between the two air one tone fule the next I have 37k on my 21 Sports and 2500 on my 22 JTRD Gecko

 

[Outback_Joe]

Something else you may be experiencing is that cold weather takes a little more fuel to get the engine and everything else up to temperature. My mileage has dropped with the drop in temperature in the last month.

 

[fourfa]

Most of you seem to have glossed over the OP's GFC, a permanently installed camper that sticks up above the cab for permanent extra air resistance and weight. Sorry to say (since rattling off your own personal MPG history seems to be a favorite pastime of this board) but anyone with an open bed is not very relevant here

I put a heavy Alu-Cab camper on my JTRD two months after getting the truck, 37s and a weighty lift 6 months after that, then a slowly increasing amount of gear and furnishings permanently installed in the camper. The weight adds up, and it really matters. You're welcome to browse my MPG history, which seems a lot more relevant to yours than most here:

https://www.fuelly.com/car/jeep/gladiator/2022/fourfa/1156647

Broadly similar to what you're reporting. Lately in pure city 17 isn't unusual, and the max I see on the freeway is 22-23. Overall combined 19-20. All taken from obsessively corrected odometer (calibrated by long GPS distance tracks, disconnected from the truck GPS)

As for the sudden drop, yeah most likely winter diesel. Track it over a few years and it'll probably show up every year.

 

[Wolf Island Diver]

35 psi seems high but that shouldn’t hurt MPGs. I chalk tested my 37s, albeit KM3s which is a different tire and I run around 27-28PSI.

With all my bullshit bolted on (rack, awning, bed full of overlanding junk) I can easily get 27 @ 70MPH and 30ish @ 65MPH. It get combined 22MPG but I drive like a bat outta hell. The torque of the diesel turns me into Mr. Wheeler doing 85 down the interstate.

Going to 37s, I saw a noticeable drop. But if you haven’t changed anything, I’d be concerned that something is wrong seeing dropping MPGs. It might be due for an ecu update/flash.

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