Jeep has an unusual history when it comes to engines. The brand’s ownership has changed hands more times than a Honus Wagner baseball card, and in the process it has been subject to the whims and best laid plans of companies that didn’t always have the best financial conditions or technical resources.
What are the more compelling Jeep powerplants that have emerged from this collection of mixed mechanical DNA? Here are our picks for the best Jeep engines of all time.
Willys Go Devil
The original Willys Jeep was built for the US Armed Forces as a go anywhere that saw action during World War II. The civilian Jeep, or “CJ,” helped popularize off-roading as a post-war pastime, and a big part of that vehicle’s appeal was its battle-tested engine, the four-cylinder Go Devil.
Evolving over a five-year period from a low-drive, economy-focused engine to an extremely reliable, torque-happy military-spec engine, the Go Devil produced around 60 hp and 105 lb-ft of twist from its 134 cu.in. displacement. The Go Devil made an almost seamless transition to civilian life, where it received an improved cooling system and a smoother crankshaft to help it fit better on country roads.
The engine remained in production until 1952, when the Willys Hurricane took over—no, not the twin-turbo inline-six headed under the hood of the new Jeep Grand Wagoneer, but the original four- and six-cylinder flats, which provided a substantial increase in power over the original Go Devil design thanks to their improved breathability and higher compression ratio.
The largest V8 ever fitted to any Jeep model was the AMC 401. The ultimate version of American Motor’s eight-cylinder architecture, the 401 was offered in a number of guises (including the Javelin muscle car) in addition to its use in the full-size Jeep ( Wagoneer, Cherokee and J-Series pickups).
The 401 cubic inch engine represented the third generation V8 built by AMC, developed from the 390 CID that had never made it into a Jeep, and with forged rods and a forged crankshaft. Output varied from 330 horses to under 200 ponies in the late 1970s after emissions equipment had suffocated the engine from its glory days. Torque peaked at just over 400 lb-ft. Like most great engines of the era, the 401 ended up under the hood of Jeep’s largest SUVs, as rising fuel costs had pushed it out of the passenger car mix entirely by 1977.
Of all the Jeep engines in the world, the 4.0L inline six is by far the most famous. One of the last engines to be developed by AMC, it debuted in 1986 as the most powerful option available from the XJ-generation Cherokee, and it remained in the Jeep lineup through not one, not two, but three changes in company ownership. for the next 20 years of Jeep history.
What is it about the Jeep 4.0 that has made it so popular with owners and enthusiasts alike?
In one word: reliability. The 4.0 I6 has a reputation as an immortal engine, one that can take massive amounts of abuse (and mileage) and keep ticking. By the early 1990s, the engine was good for a respectable 190 hp (in High Output trim), and it had spread across the lineup to be available in the larger Grand Cherokee, the Comanche pickup, and the iconic Wrangler.
3.6L Pentastar V6
Following the demise of the 4.0, Jeep’s six-cylinder fortunes languished for a few years as parent Chrysler tried to close the gap with the workman-like but ultimately uninspiring V6 originally offered with the brand’s minivan. In 2012, however, a new bright spot appeared on the horizon in the form of the Chrysler 3.6L Pentastar V6.
Let’s be clear: the Pentastar is not an “exciting” engine. That said, with 285 hp and 260 lb-ft of torque on tap, it provided a huge upgrade over the engine it replaced, with a fuel mileage bonus to match. One of the last pieces of the modernization puzzle that the JK-generation Wrangler had attempted to put together, the Pentastar was also offered as the entry-level engine for the Grand Cherokee (with a smaller displacement version found in the compact Cherokee).
3.0L Turbo Diesel V6
Jeep was one of the first domestic SUV builders to use diesel, starting with a common rail engine in the late 2000s. By the middle of the following decade, it had significantly improved its turbodiesel range thanks to Fiat-Chrysler’s ties to Italian engine builder VM Motori.
The result was the 3.0L “EcoDiesel”, an engine that could be used with the Grand Cherokee (and much later the Wrangler and Gladiator). With 240 hp and 420 lb-ft of torque, the turbodiesel unit was capable of 30 highway miles per gallon, representing a big step up in efficiency for Jeep’s larger options without any real significant drop in performance. No other American sport utility vehicle of similar size has been able to match that level of frugality and muscle.