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For decades, diehard Jeep CJ and Wrangler fans in the U.S. have prayed for the low-end torque and high(er) fuel economy of a diesel engine, and for decades they have been denied. That is, until now; the 2020 Jeep Wrangler EcoDiesel ends the drought by bringing absurd off-road capability and the best fuel efficiency ever seen in a Wrangler. But it comes at a dear cost.

(Full Disclosure: Jeep flew me to Zion National Park in Utah, fed me lots of food that I shouldn’t have eaten since I’m on a diet, and put me up in a hotel with two large beds and a kitchen. Also, I should say that I formerly worked for Fiat Chrysler on the JL program, though almost entirely on the gas variants).

Say the word “diesel” to a crowd of Jeep enthusiasts, and a pool of saliva will form as they daydream about a Wrangler with enough low-RPM torque to idle up a mountain, and enough fuel economy to travel literally tens of miles on a single fill-up. Yes, the diesel engine has been Jeep fans’ holy grail for a while, and yet, aside from some rare CJ-5s and CJ-6s from the 1960s, some obscure CJ-10s from the 1980s, and various vehicles sold in other countries, convertible successors to the heroic World War II Jeep have always used gasoline for propulsion. That’s why the 2020 Jeep Wrangler EcoDiesel is such a big deal.

Did Jeep answer the diehards’ callings with the new engine? In some ways, yes; the Wrangler EcoDiesel delivers decent fuel economy and helps the Wrangler absolutely destroy its rivals in terms of raw off-road capability. But sadly, it also comes with significant drawbacks.

What Is It?

By now, you’ve probably read all about the “JL,” the latest generation Jeep Wrangler that launched for the 2018 model year. It’s a body-on-frame SUV that’s not great on-road thanks to its dual solid axle suspension setup, old-school steering box, and rather un-aerodynamic shape. But it’s incredible off-road, and it’s hugely improved over its “JK” predecessor, with better fuel economy, a nicer interior, prettier looks, more comfortable on-road dynamics, smart changes to usability, and the list goes on.

The 2020 Jeep Wrangler EcoDiesel is largely the same as every other JL, except its engine bay houses the 3.0-liter “third-generation” EcoDiesel found in the new Ram 1500 EcoDiesel. That motor replaces a 3.0-liter “second generation” diesel offered in Jeep Grand Cherokees and older-generation Ram 1500s, and gets so many changes over the old mill that parent company Fiat Chrysler refers to it as “all-new.”

You can read our recent Ram 1500 EcoDiesel review if you want to learn about the 60-degree V6 engine’s changes over its predecessor, but for now, let’s look at what Jeep had to do to the Wrangler to fit the diesel motor, and also what the company had to do to the motor to make it fit the Wrangler.

The 2020 Jeep Wrangler EcoDiesel makes 260 horsepower and 442 lb-ft of torque. Compared to the Wrangler’s 3.6-liter naturally aspirated V6 (285 HP, 260 lb-ft) and 2.0-liter turbo inline-four (270 HP, 295 lb-ft), that’s down only a bit on power, but way up on torque.

The figures are impressive, which is good, because the diesel and its ancillary components add about 400 pounds over the gas options, with the lightest 3.0-liter diesel JL Sport weighing in at a claimed 4,654 pounds. The heft, as the Wrangler’s chief engineer Pete Milosavlevski (“Milo” for short) told me, necessitated a roughly 10 percent stiffer suspension spring rate. He also said that, in order to improve jounce control (particularly to prevent the suspension from “bottoming out”), even Sport and Sahara EcoDiesels sit at the same elevated suspension height as Rubicon trims (on gas variants, the Rubicons sit about an inch higher than Sport and Sahara). It’s worth noting that overall ground clearance does still vary between trims due to differences in tire size.

You might have noticed from the aforementioned curb weight figure that the diesel Jeep Wrangler JL does not come in two-door guise. This, to diehard Jeep enthusiasts like myself who aren’t fans of the four-door’s giant belly and its associated small breakover angle (not to mention its lack of pedigree), is a huge disappointment. But it’s not nearly as disappointing as the fact that the JL diesel comes only with the automatic transmission.

When Jeep diehards dreamt of a Wrangler diesel over the past 50 years, they probably envisioned a small, nimble off-roader with a stick-shift, and not a 4,600-plus pound four-door behemoth with a competent but hardly exciting eight-speed auto. They also probably didn’t anticipate a $39,290 base price (including destination), which is $6,000 over the base four-door manual Sport, $4,500 over the automatic 2.0-liter turbo, and $3,350 over the automatic 3.6-liter.

You might also have noticed that the 442 lb-ft torque figure, which is made all the way down at 1,400 RPM, is lower than the 480 lb-ft on the Ram. According to Milo, this is the result of the Wrangler having a rear differential with a smaller ring gear and thus lower torque capacity than that of the DT Ram.

Speaking of differentials, all JL diesels regardless of trim receive the 220 mm rear axle ring gear and the 210 mm front ring gear normally reserved for Rubicon trims on gas variants. Non-Rubicon gas Wranglers have a 186 mm ring gear up front and 200 mm ring gear out back. (Plus, gas Wranglers are offered with various axle ratios, while the EcoDiesel gets 3.73 gearing across all trims).

It’s not just torque output that makes the JL’s 3.0-liter engine different than the Ram’s. Jeep says it moved the alternator to a higher location to help with water fording, and that this necessitated moving the injection pump to the driver’s side of the engine. In addition, the intake and exhaust are quite different than the Ram’s, as is the oil pan shape due to different packaging constraints.

There are quite a few other changes that Fiat Chrysler engineers had to make to the Wrangler to accommodate the diesel motor. An 8HP75 eight-speed automatic transmission offers a higher torque capacity than the 850RE in the gas models; the fuel tank is smaller at 18.3 gallons versus 21.5 on gas models (Milo told me this is due to the diesel’s 5.1-gallon urea tank, which takes up precious packaging space under the vehicle—see update below); the hydro engine mounts are specifically tuned for the diesel (but are based on the 2.0-liter’s mounts); shock-tuning has changed; firewall sound-deadening and other enablers have been implemented to reduce noise, vibration, and harshness; and a number of new skid plates have been installed to protect precious fuel-system and emissions components.

Update about the fuel tank size: A Fiat Chrysler spokesperson told me that the urea tank isn’t the main reason why the Wrangler EcoDiesel’s fuel tank is smaller than that of the gas Wranger. From FCA:

“The biggest factor contributing to the smaller fuel tank size on the 3.0L EcoDiesel (compared to gas engines) is the t-case, not the urea tank. On the 3.0L EcoDiesel, the exhaust system / SCR runs along the passenger side of the vehicle, which pushes fuel tank to the driver side. The front propshaft also attaches to the t-case toward the driver side. So there is less packaging room for the 3.0L fuel tank, compared to the gas engine vehicles which have the fuel tank on the passenger side.”

Street Driving In A Sahara

Jeep had a giant lineup of Saharas sitting on a baseball field for journalists to choose from. My drive partner and I snagged the $56,030 white one shown below, and prepared to follow Jeep’s pre-set route that would take us on the highway and then on a low-speed cruise through Zion National Park.

I hopped into the driver’s seat, placed my right foot on the brake pedal, and pressed the start button with my right index finger. The 3.0-liter diesel motor jumped to life with a high-pitched sound similar to that of a horse’s neigh and then emitted a low-frequency rumble similar to that of a large cat purring once the engine had reached a steady RPM.

A light “clacking” diesel-y noise could be heard when driving at low speeds, but it wasn’t harsh. At higher speeds, the engine could only be heard under high RPMs but was otherwise drowned out by wind noise as oncoming airflow seemed to struggle to flow around the Jeep’s upright windshield and tall, squared-off mirrors.

Driving through Utah’s gorgeous, twisty roads, the Jeep handled like others I had driven. Brake dive, body roll, and steering play were significant, and steering response was far from immediate. What surprised me, though, was the ride quality, which on my vehicle somehow seemed worse than other four-door JL Wranglers I had driven, with the Jeep somehow yielding a jittery ride over what appeared to be glass-smooth roads.

I’d be surprised if 10 percent stiffer springs, retuned dampers, and the roughly 10 percent too-high tire pressures that I noticed in my press vehicle would have that much of an effect on the ride compared to a gas Wrangler Unlimited. I’d like to drive a gas and that diesel back-to-back to better investigate further, but it’s still worth a note. Because one of my main takeaways from the on-road portion of this drive was how small imperfections in the road seemed to upset the Jeep. I later drove a Rubicon model on the street, and it seemed to ride better. For now, I’m a bit stumped.

While cruising at a steady speed, hammering the fuel pedal yielded a distinct “one-two” punch from the downshift followed by the kick from the engine’s boost. Unsurprisingly, yanking the 8HP75 transmission into a lower gear and then hammering the accelerator pedal yielded significantly better response, and frankly, some decent acceleration.

My expectations for diesel engines comes from my experience driving the Chevrolet Colorado ZR2 diesel and the Ram 1500 EcoDiesel. In each of those trucks, the diesel is significantly less powerful than other engine offerings, but also makes more torque. As a result, choosing the diesel requires a sacrifice in acceleration performance, especially on the highway.

In the JL, things are a bit different. The 3.0-liter’s 442 lb-ft of low-end grunt helped my Wrangler Sahara not only hold eighth gear up hills at highway speeds, but, after I manually locked into the top gear, the Jeep even accelerated up the grades! Yes, in eighth gear—one that you rarely see in the gas JL when climbing any incline. With the pedal to the floor, the diesel just happily chugged along at a low RPM and forced the vehicle up the slopes with pure brawn.

What’s more, coming to a stop on the road, pressing the brake pedal, and touching the speed-pedal began what—had it not been for the stability control putting an end to the fun after a few seconds—would have been the slowest (i.e. lowest wheel angular angular velocity) burnout in history.

But the torque isn’t what surprised me. I expected tidal waves of torque. But what I didn’t expect was the 3.0-liter diesel Wrangler to feel genuinely quick (in the context of Jeep Wranglers). Honestly, I’d be surprised if it was much slower to its gas counterparts.

On a few occasions, I brought the Jeep to a stop and then hammered the accelerator to the floor just to see how quickly the boxy machine could get up to speed. On one launch, I noticed a clunky shift out of first gear, but otherwise the eight-speed, along with the diesel motor, moved the heavyweight Jeep with vigor.

I did also notice that quickly letting off the pedal from a high-load condition, like when I accelerated up hills in eighth gear, emitted a burp from the rear of the Jeep—one that the EcoDiesel engine’s chief engineer Mauro Puglia told me was almost certainly caused by a flap in the exhaust. That flap isn’t there to offer various exhaust noise settings like it is in sports cars, its job is to create a restriction in order to establish a higher pressure aft of the diesel particulate filter where the low-pressure EGR—an emissions reduction device—pull exhaust gases that it ultimately sends to the intake. This leads to a higher pressure differential and thus better EGR flow.

The good news is that the “burp” wasn’t really a problem. It was there, but hardly overly loud or annoying.

Fuel economy figures were great for a Wrangler. The Sahara I drove from our morning staging area in Springdale, Utah to the lunch spot/off-road course, Sand Hollow State Park roughly 35 miles away, averaged over 30 mpg for a good portion of our drive. And while I didn’t record that vehicle’s average over a distance, I did score 27.7 mpg over a 34 mile trip in the less efficient Rubicon model.

Official fuel economy numbers aren’t out yet, but Jeep says its targets lie somewhere near the EPA figures for the 2020 Ram 1500 EcoDiesel 4x4 and the 2019 Jeep Grand Cherokee EcoDiesel 4x4, which scored 29 mpg and 28 mpg highway, respectively.

Off-Roading In A Rubicon

Jeep let journalists drive the Wrangler through a fairly difficult off-road course consisting of a bit of sand and lots of rock beds. The washboard-like sand trails bounced the two Dana 44 solid axles up and down and made for a bouncy and harsh ride, but that is the extent of any complaints I had about the JL diesel off-road. Because it was truly a monster.

You may think this isn’t a surprising revelation—a diesel Wrangler should be a beast off-road. But there’s a lot that could have gone wrong; my biggest concern was low-speed throttle response.

On both the Chevy Colorado ZR2 diesel and the Ram Rebel EcoDiesel, trying to crawl up and over obstacles at low speeds required an alert left foot to feather the brake pedal, as both vehicles tended to rev their engines to build torque, and then when a wave of it hit, I found myself driving much too fast. The only way to crawl extremely slowly over rocks in a controlled manner was to left-foot brake.

I worried that the JL would suffer from the same ailment, but I quickly learned that it just doesn’t. The Rubicon model, with its four-to-one low-range transfer case gearing, 4.71-to-one first gear ratio, and 3.73 axle ratio (that’s taller than the 4.10 that the gas Rubicon has—Milo says this was done for fuel economy purposes) has a 70-to-one crawl ratio. Between that, and the way Jeep dialed in the pedal response to be less sensitive in low-range, I was able to tip into the throttle a tiny bit and crawl the Wrangler EcoDiesel up steep grades at incredibly low speeds with stellar control.

In fact, driving the Wrangler—with its tremendous suspension articulation, small overhangs, and high ground clearance—through the off-road trail in low-range felt like such a cheat code that, just for fun, I tried the whole course in high-range with the differentials unlocked. From a standstill, I started my ascent up steep grades and over large rocks; the engine clacked louder and louder as the revs built up past 1,500 RPM, then the turbo whistle chimed in and the Jeep crawled right up whatever was in front of those 33-inch BFG all-terrain tires.

I rarely saw the revs crest 2,000, and though I had to left-foot brake some to keep the Jeep under control, the fact that I could comfortably rock crawl in high-range is a testament to the engine’s tremendous low-end torque.

The other area where I was concerned was underbody protection. The Wrangler EcoDiesel has a bunch of emissions-related underbody components that would be expensive to replace if damaged off-road. For example, there’s the 5.1-gallon urea tank (incidentally, Jeep says the urea fill lasts up to 10,000 miles) that hangs off the back of the Jeep aft of the rear axle, plus there are various exhaust components meant to scrub nasty pollutants out of the exhaust stream. On top of that, a fuel-water separator (a filter charged with removing water and other contaminants from fuel) hangs low under the Jeep’s belly.

The good news is that Jeep has wrapped those vulnerable parts with steel skid plates. You can see the one for the urea tank above, and here’s the one for the fuel-water separator. Notice how it’s been scratched up a bit:

And here you can see the skid plate for the exhaust, just on the other side of the driveshaft from the fuel tank and transfer case skid plate:

By and large, everything looks well protected, though the muffler at the very back looks a bit like rock-bait, and I am a little concerned about the transmission oil pan:

The engine oil pan, there on the left, isn’t as much of a concern since it’s essentially right above the front axle, but I could see the transmission pan, which admittedly sits rather high, getting a ding or two. I asked the chief engineer about this, and he said this wasn’t an issue in validation testing.

Early Verdict

The Jeep Wrangler EcoDiesel is an absolute off-road beast, but it’s also a huge compromise. Just opting for the engine costs $6,000 over the base 3.6-liter Wrangler Unlimited with a manual transmission and $4,500 over the 2.0-liter automatic. That’s a ton of cash that you’re not likely to ever make back in fuel savings.

To drive that point home, let’s just say the Wrangler scores the same fuel economy as the more slippery Ram DT whose EPA numbers Jeep is targeting. According to the EPA, annual fuel costs for that truck total $1,900. Annual fuel expenditures on a 2.0-liter turbo Wrangler Unlimited are $1,850, so you’re not saving money. Granted, if you spend most of your time driving on the highway, you might actually save cash on fuel, and it’s worth noting that real-world and EPA numbers are often not the same. Plus, if you tow, you might see a larger gap between the diesel’s fuel economy and the gas engine’s, but that brings me to another drawback: The diesel Wrangler doesn’t tow any more than the gas model. Still 3,500 pounds.

So if you’re considering the diesel to save money long-term, don’t.

Other drawbacks include a significantly higher curb weight, the slight annoyance of having to refill urea, and lower-hanging underbody components.

Still, the torque is incredible, especially off-road where, in low-range, this Jeep crawls with true precision. Plus, the vehicle doesn’t significantly sacrifice acceleration over gas Wranglers, and despite its smaller fuel tank, you can expect a cruising range of over 500 miles.

I’m still disappointed there’s no two-door and no manual, but if you’re looking for a four-door, automatic off-road beast—especially one to lift and put giant tires on—this EcoDiesel will make you very, very happy.

Update Nov. 16, 2019 7:50 P.M. ET: Fiat Chrysler has responded to my earlier inquiry asking about how it is that the the urea tank—which sits aft of the rear axle—reduces fuel tank size, since the tank sits between the axls.

Sr. Technical Editor, Jalopnik. Always interested in hearing from auto engineers—email me. Cars: Willys CJ-2A ('48), Jeep J10 ('85), Jeep Cherokee ('79, '91, '92, '00), Jeep Grand Cherokee 5spd ('94).

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