The wind is picking up and the sun is already sliding behind the hills when we decide to climb the big hill one last time. The hill with tire-grabbing ruts and slick, crumbly limestone near its top. The one that bottoms out most trucks, stopping them dead in their tracks about 50 feet from the crest. The 2020 Jeep Wrangler EcoDiesel had already tackled it twice today, making it up the steep grade like it was a suburban driveway. With the temperature dropping and the light quickly fading, its 442 pound-feet of torque and locked front and rear differentials get us to the top once more—just in time to watch the orange fireball drop below the curvature of the earth.
Our day playing in the dirt is over, and the diesel-powered Jeep Wrangler, the first-ever offered in North America, has proven itself worth the wait.
True, Jeep did offer a 62-horsepower four-cylinder diesel in the CJ-5 back in the 1960s, but according to Jeep, the 2020 Wrangler EcoDiesel is stateside because of overwhelming consumer demand. Jeep sells about 200,000 Wranglers a year and the vast majority of those are four-doors. If you want a diesel-powered two-door Wrangler, though, you’re out of luck. The turbocharged 260-hp 3.0-liter diesel V-6 is limited to the more popular four-door models, but it is available in all trim levels.
This is the third generation of an engine both Jeep and Ram have used before. It’s produced by FCA’s engine subsidiary VM Motori in Cento, Italy, and Jeep says about 80 percent of its parts are new, including its compacted graphite iron engine block, which is 15 pounds lighter. Other changes include new aluminum cylinder heads with improved flow, redesigned 29,000-psi fuel injectors, and a new lighter set of aluminum pistons with thinner rings and a low-friction, diamond-like carbon coating to reduce parasitic losses. A more efficient variable-geometry turbocharger creates more boost, now 31.9 pounds, and less lag. It’s essentially the same engine currently offered in the Ram 1500 pickup; however, Jeep lowered its compression ratio from 16.5:1 from 16.0:1 to reduce noise and improve fuel economy.
Getting the engine into the Wrangler wasn’t exactly a bolt-in job. There were complications. First, a place for a 5.1-gallon diesel exhaust fluid (DEF) tank had to be found. It’s fitted behind the fuel tank, which had to be made smaller to compensate; Diesel Jeeps have an 18.3-gallon tank, while gas-powered models have a 21.5-gallon unit. Jeep points out that DEF refills align with oil changes about every 10,000 miles. More importantly, the Wrangler’s off-road capability had to be maintained—including its ability to drive through 30 inches of water—which meant relocating the alternator, air intake, and exhaust.
The diesel’s substantial torque output, which peaks at just 1400 rpm, also proved to be an issue. Some of the Jeep’s drivetrain components just couldn’t handle the additional twist, including its standard six-speed manual and ZF-supplied 850RE eight-speed automatic. To fix this every Wrangler EcoDiesel gets ZF’s beefier 8HP75 automatic, the same eight-speed used in the Ram, and diesel-powered Sport and Sahara models use tougher Dana 44 axles front and rear from the Rubicon, along with a 3.73:1 gear ratio.
To handle the diesel’s additional 400 pounds the Jeep’s suspension also had to be retuned, and some of its ride quality has been sacrificed. Spring rates are 10-percent stiffer front and rear and new firmer dampers are used. Although the ride is noticeably firmer than on gas-powered models, it isn’t uncomfortable and articulation isn’t diminished off-road. The Wrangler’s ground clearance numbers, 10.8 inches on our Rubicon, remain unchanged.
Although noisier than the Jeep’s standard 285-horsepower 3.6-liter V-6, or its available 270-horsepower turbocharged four-cylinder, the EcoDiesel’s refinement will surprise you. The engine is smooth and idles with very little clatter. It’s a bit slower than the gas-powered models off the line, but not enough to matter, getting the nearly-5000-pound Jeep to 60 mph in less than seven seconds. When off-road, its low-end torque peak, which lasts until 2800 rpm, noticeably improves the Jeep’s low-speed crawling and climbing abilities.
Its other advantages are fuel economy and range. Its EPA ratings of 22 mpg city, 29 mpg highway and 25 mpg combined make it the most fuel-efficient of the Wrangler’s available powertrains, and despite its smaller fuel tank, its potential range of over 500 miles on the highway will make it a favorite with the overlander crowd.
But it ain’t cheap. The engine costs $4000 over the standard V-6, and the required automatic is another $2000. The least expensive diesel Wrangler will cost you about $40,000 and our test vehicle was well over $50,000. Although Jeep is expecting more than ten percent of Wrangler buyers to pay up for the EcoDiesel, we don’t really recommend it. Unless you plan to traverse a third-world jungle or you’re headed for Russia and the Road of Bones, you may be better served by saving the $6000 and sticking with the standard V-6. It’s more than powerful enough, its fuel mileage is respectable, and it runs happily on cheap 87 octane. Plus, it’s available with a manual.
Now if Jeep will just get down to business and install its 707-horsepower supercharged 6.2-liter V-8 in the Wrangler. Yup, it fits.