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13.2 mpg with 37s....

40”JLURD

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What you're not accounting for in your equation is the initial cost of the Diesel engine over the base engine. I just built two identical JLUR's on the Jeep site, selecting no options for one with base engine and only the diesel option (which included some mandatory options) for the other. The diesel equipped JLUR cost $49,885 and gas equipped was $43,885. That's a $6,000 difference for a diesel Wrangler. A third optional build is with the 2.0T engine and automatic transmission at $45385. That's still $4,600 cheaper than the diesel.

Based upon your math (which I did not check as I assume it's correct), I can drive the base gas engine 100k miles before I would break even on the cost of the diesel equipped Wrangler. Or I can drive roughly 75k miles on the 2.0T with auto before reaching the cost of the diesel option.

This doesn't take into account the higher maintenance costs of the Diesel engine either......more frequent fuel filter changes, oil changes cost more due to larger oil capacity, DEF, etc.

I'm not degrading the Diesel engine. For those who don't necessarily need a diesel, it can be hard to justify the higher initial cost when it takes a long time (and at least 100k miles) to recoup the initial premium cost vs. a gasoline engine.
That’s why I said.

“So depending on how long you want to keep your Jeep you may want to consider trading in for the diesel motor if MPG with 37’s is a concern.

DEF usage is typically about 3% of your diesel usage. So 2,083.33 x 0.03 = 62.49 gallons of DEF - let’s call it 62.5

Home depot and Target sell the 2.5 gallon jugs for $12.50 of Blue Def. That’s a good name brand. It can be had way cheaper if you buy a cheaper brand. Or even cheaper than that if you fill it up at a truck stop from the pump. It’s less than $3 a gal there. But let’s say you buy the Blue Def for $12.50 even though there are cheaper options.

62.5 / 2.5 = 25 (jugs of blue def to go 50k) 25 x $12.5 is only $312.50 DEF cost for 50,000 miles. If you divide the $312.50 by the 2083.33 gallons it adds about 0.15 per gal to your operating costs, or $2.70 per fill up. Not the end of the world especially when your getting almost double the MPG.

No this still doesn’t make it a cheaper power plant. But IMHO it greatly offsets the initial investment if you are going to keep your Jeep to 100k or beyond.

Not to mention the gobs of extra torque you will enjoy the entire time you own it, and the ease at which it keeps even 8th gear going uphill on the highways. There are several advantages to the diesel which I feel like justified the extra price for me at least.

To each their own though. Enjoy your Jeep’s friends
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lepcat

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There's something else going on - I'm running 37's, 3 1/2" lift, metal bumpers + winch, skid plates on the V6 and getting 16. You should be getting at least the same. I think there's a thread somewhere showing everyone's MPG if you can find it.
Did you reprogram the tire size?
 

Kurt0

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Im in a Glad Mojave On 37” Falken AT’s; Pulsar programmed tire size. Last 240mi my all combined mpg in “Performance” mode has been 19mpg. Stock 4.1 gears.
 

JimLee

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All of this is very subjective. I usually average around 18MPG around town, one day of being in a hurry and making multiple stops drops it to 15 real fast.
 

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Varilux

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I was getting about 18mpg (3.6L) on the highway with the stock Rubicon 33" tires and 4.10 gears. I switched out to 37x12" RidgeGrapplers and that dropped the mpg to around 14-15 (and I very rarely saw 8th gear).

Switched to 4.88 gears, and power is great and I'm seeing 8th gear routinely again. However, as mentioned the mpg is still around 14.5mpg (and if we're going to the cabin, where average speed is 75mph or so that drops to around 13mpg.

End of day- worth every penny. Love the extra clearance (and looks pretty good too).
 

RELBUS

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This thread makes me glad I got a diesel. Guys are getting 24mpg on stock gears with 37’s all day long on those motors.

Looks like the ole “you’ll never make that motor cost up in fuel savings” wives tale may not hold up so well with 37’s or larger. At 10mpg +/- that’s a huge delta between the two motors.

At 13.2 mpg it would take 3,787.87 gallons of gas to drive 50,000 miles.

At 24 mpg it would only take 2,083.33 gallons of diesel to go the same 50k

Average Oregon Gas Price is $2.59
Average Oregon Diesel Price is $3.27

$2.59 x 3,787.87 = $9,810.58 Gas Cost

$3.27 x 2,083.33 = $6,812.49 Diesel Cost

Fuel Savings in 50k miles = $2,998.09

So depending on how long you want to keep your Jeep you may want to consider trading in for the diesel motor if MPG with 37’s is a concern.
Love diesels, and wish the option had been available at the time I bought.
It would be interesting to see DEF, fuel filters, and any other additional maint. requirements factored in to the equation.

I have owned numerous Ram Cummins, and currently own one...and they definitely cost substantially more to maintain!
 

Iggy

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well, then that’s about right. Gears appear to cost about $800. Just have to see what the install process is and save
Word of caution: Installing gears is not a bolt on process for an afternoon. Before buying into doing it yourself, research articles written about installing new gears. It's an entailed project requiring measuring with dial indicators, shimming, re-measuring, etc. A professional mechanic would be my choice.

Your stock tire diameter (285/70x17) was probably about 32.7". You have 4.10 gears. A true 37" tire (many are 36+/-") will be the same as having 3.64:1 gears, about an 11% change from stock. My 2.0T JLU with 3.45:1 gears on 32.9" BFG KO2s works fine at 4,600' and gets an average of 21 MPG. The bite into your acceleration and MPG is the weight of the tire and 20" wheels, and the tread pattern.

At 88 pounds for each tire, opposed to around 58 pounds for a stock 285/70x17 BFG KO2, that's an increase of 30 pounds per corner. You've just added 120 pounds to the reciprocating mass that engine needs to overcome at all speeds. That's a 51% increase in mass! Adding gears won't give you any relief for MPG. The weight is what ate your lunch. You'll take longer to stop and your pads will wear out much quicker, too. This doesn't begin to touch on the tread design.

I'll bet it looks good, though!
 

SoK66

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2021 JLUR, hard top. Plastic bumpers. 35” spare.

tires -37x13.50r20 Nitto Mud Grapplers.

Mostly city driving, commute to work.

I expected a decrease from the 37s, but 13.2 is pretty bad.

ive considered an intake and exhaust, maybe a tuner and gears in the future.
Thoughts??
13.2, that good huh? 😂
 

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MichaelAnthony

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Well when I switched over to Cooper STT Pros 37x13.50x17 my mileage went to 12.5 mpg and when my foot gets in the way it drops down real quick. Also all of my traveling isn't flat land....... living in the Appalachian up and down these hills the mileage isn't very good any way....
 

Whiskey 13

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Let me see if I got this right. I buy a vehicle with the aero dynamics of a brick. When I get it home I rip off the plastic bumper, throw on a big metal bumper and that bad to the bone winch. Then I take off the small light street tires put a 4 inch lift, lockers, disconnects, and my brag factor 37 inch mudders on it to help with the aero dynamics of course. I then add some nice heavy rock sliders and a steel rear bumper along with the roof rack. Then I make sure I have 4.10 or lower gears and all the other goodies to make me look cool at the mall. Then I wonder why I get less than 15 MPG as I take my super extremely 4 wheel drive capable monster to the dog park.
 

Yellowssm

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Currently on this tank with 50/50 city/hwy. Not bad for a brick.

F0B7E9D9-F6B2-4606-AD40-254AF8CC995D.jpeg
 

BHo

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I’m on 4.10:1 gears with BFG 37x12.50R17 at 32psi. I verified my tire size by doing a circumferential rollout C/π = d, programmed my flash calibration tool to the true diameter, verified speedometer with GPS.
I don’t push hard on the throttle and do interstate between 65-75 mph. Currently, I’m getting 18-20mpg on Highway and 16-17mpg city. I’ve been monitoring for the past 6 months.
8B997D95-0090-4033-A66D-AE4BFB3249C1.jpeg
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