For Moving Mountains, or Climbing Them, Jeep’s Wrangler Goes Diesel

ST. GEORGE, Utah — Jeep has been on this quest for decades — “the Holy Grail,” said Jim Morrison, the marque’s boss since June — for a diesel engine suitable for the Wrangler.

“Since I’ve been in this job, the three things Jeep customers keep telling me they want are a pickup truck, a diesel in a Wrangler and the return of the Wagoneer,” Mr. Morrison said last month at a media event in Utah. “We delivered on the truck with the introduction of the Gladiator. Here, we’re unveiling the first Wrangler EcoDiesel. No comment on the Wagoneer.”

He added: “The customers were right. This version of the Wrangler has the perfect mix of driving dynamics, four-by-four capability, fuel economy and torque.”

In a way, it has made little sense that the Wrangler never had a diesel option in its decades of existence. Gasoline engines are suited for speed — which the boxy, high-riding Wrangler itself is not. Gas engines get inherently worse fuel economy.

And they generally don’t have the “oomph” needed for grunt work like pulling stumps, clambering up hills and scrambling over rough terrain. Those jobs call for diesel power.

But that power has a drawback, too: emissions. Fiat Chrysler of America, Jeep’s parent company, is betting it can pass ever-more-stringent tests, a wager of hundreds of millions of dollars. It has passed the needed certification; it should go on sale in time for the first few to end up in driveways on Christmas morning with a red bow on the hood. It will then need to win over shoppers.

In January, Fiat Chrysler agreed to pay hundreds of millions of dollars to settle lawsuits accusing it of using illegal software to pass emissions tests for certain diesel pickups and Jeeps. A senior manager is facing federal fraud charges in the episode.

While diesel has drawbacks — the engines burn fuel efficiently and produce less planet-warming carbon dioxide, but they also emit more nitrogen oxides, which can cause asthma and other serious lung ailments — it is the fuel of choice when brawn is needed. Fiat Chrysler believes it has the best of both worlds with a cleaner EcoDiesel engine.

“This thing has earth-chewing torque,” said Pete Milo, a Fiat Chrysler engineer. “It can conquer any obstacle.”

Mr. Morrison was coy about fuel-efficiency numbers, but he did concede that this EcoDiesel was generally 30 percent more fuel efficient than a gas equivalent. That translates into an extra seven or eight miles per gallon. In a lengthy test drive, the Wrangler got nearly 30 m.p.g. in mixed highway and city use.

Since the first EcoDiesel appeared in 2011, Fiat Chrysler has been trying to perfect it for use in vehicles like its Ram pickups and the Wrangler, where customer demand has been vocal. But results have been mixed. A second generation, introduced in 2014, promised improvements in reliability, fuel economy and emissions. It didn’t deliver.

Installed in 2014-16 Ram pickups and Jeep Grand Cherokees, the wayward second-generation EcoDiesel was pulled from the market when it was found to be in violation of emissions standards. A negotiated settlement with the government, which required a recall of the affected vehicles, revamped emissions controls, extended warranties and $3,000-plus payments to owners, took nearly a billion-dollar bite out of the company’s bottom line. (Just last month, Fiat Chrysler had to recall an additional 108,000 Ram EcoDiesels from the 2014-19 model years for exhaust gas recirculation cooler cracks and system leaks.)

The problematic EcoDiesel effectively deprived the company of the kind of diesel offering it needed at a time when Ford and General Motors were enjoying strong sales of their diesel-equipped trucks (albeit with their own shares of reliability and emissions-related issues).

So, back in 2015, the diesel specialist Mauro Puglia, at Fiat’s V.M. Motori engine works in Cento, Italy, was tasked with coming up with a viable replacement, capable of meeting ever-stiffer emissions rules.

Now, four years later, Mr. Puglia said his work was complete. In automotive development circles, the four-year timeline could be considered something of a rush order.

“I am now ready to go home. I have been here in America for three years, plus another year in Italy, working on perfecting this engine,” Mr. Puglia said wearily. “We had to meet very demanding targets: higher performance, higher torque, higher power, higher fuel economy, lower emissions.”

The Gen III EcoDiesel, in slightly different form, made its debut in a Ram 1500 pickup a few months ago. The version for the 2020 Wrangler took a little longer to plumb for anticipated Jeep-like duties like fording streams, bashing boulders, hauling toys and, of course, being tarted-up with thousands of combinations of accessories.

The engine is a turbocharged V6 that displaces 3.0 liters, and it is equipped with some beefier components than the Ram version. It’s a crucial 15 pounds lighter than a Gen II version — although the whole package adds up to 500 pounds to the Wrangler stock curb weight.

Crucially, for emissions compliance, it comes with an extra-large, five-gallon diesel exhaust fluid canister, with a 10,000-mile duty cycle — conveniently about the same interval as an oil change. That tank is so large Jeep had to design a special underbody skid plate piece to protect it.

The engine produces a modest 260 horsepower, but a stout 442 pounds-feet of torque.

The EcoDiesel in the Wrangler comes mated to an eight-speed automatic. Although the Ram EcoDiesel can be ordered with a six-speed manual, Jeep calculated that there would be insufficient demand for it. Also, the EcoDiesel is offered only in the four-door Wrangler, not the two-door model. That ranks as a bit of a disappointment for hard-core Jeep “overlanders” who were looking forward to being able to venture ever deeper into the outback with it.

“Ninety percent of the Wranglers we sell these days are four-door models,” Mr. Milo said. The percentage of manual transmission models is likewise low.

Jeep didn’t release expected sales figures, but Mr. Morrison believes they will be comparable to the take rate on other gasoline engines that are optional on the Wrangler.

In testing in Utah last month, the EcoDiesel provided a much-improved standard of capability for the boxy Wrangler. It offers torque-rich power delivery, especially on steep grades. Off road, no task seemed to be too tough to tame. On road, it could theoretically go more than 500 miles on a single tank — while a gasoline-powered version might struggle to travel 300 miles.

But it’s not cheap — the engine itself is a $3,000 to $4,000 upcharge. The most basic Wrangler Sport EcoDiesel starts at just under $40,000, while a fully loaded Rubicon EcoDiesel could easily top $60,000.

As to whether its emissions woes are finally behind it, only time will tell.