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2008 Jeep Grand Cherokee 3.0-liter Diesel Review

2008 Jeep Grand Cherokee Diesel

2008 Jeep Grand Cherokee 3.0-liter Diesel
More economy and morepower make green sense.

By Rex Roy
The Auto Channel
Detroit Bureau

"Don"t judge a book by itscover." You know this adage, and sometimes it even meanssomething…like learning the tattooed girl from Starbucks is a RhodesScholar. The old saying applies to the 2008 Jeep Grand Cherokee diesel,and here"s how: The Grand Cherokee last received a full makeover in 2005.

In industry parlance, this SUV is mid-cycle—another way of sayingthat its middle aged, old news, not worthy of much attention, andcompletely out of the media limelight. However, when fitted with the3.0-liter clean diesel V-6 produced by Mercedes-Benz, the Grand Cherokeesuddenly becomes a newly-relevant SUV.

With the exception of a smallbadge on the rear hatch, you"d never know this Jeep packed a huge dieselpunch while sipping fuel like a tree hugging hybrid.

It"s not that the tried-and-true Grand Cherokee isn"t a fine SUV whenpowered by any of its three gasoline-fired engines. The Jeep"s lightweightunibody and trail rated suspension deliver performance and refinement thatcompare favorably within the class of five-passenger SUVs.

Certainly,the 420-horsepower SRT-8 models lives in rarified air because of itsmind-bending acceleration and cornering performance. However —morelike HOWEVER—in 2008 the biggest newsmakers are attracting attentionby "out greening" their competition.

Fitted with a modern and efficient diesel made by Chrysler"s ex(Daimler-Benz), the Grand Cherokee can now shout "I"m green!" aslegitimately as anybody. As judged by the EPA"s more realistic testingregimes that were instituted for 2008, the diesel-powered Jeep returns mpgestimates of 17 city and 22 highway for our 4x4 model. This theoreticallydelivers a cruising range of over 450 miles from its 22-gallon tank, anumber we confirmed in our week"s test of the vehicle.

This mileagebeats every other engine offered in the Grand Cherokee line including the3.7-liter gasoline V-6. While achieving a 30-percent increase in mileage,the diesel also provides more torque (pulling power) than the GC"s optional5.7-liter Hemi.

The specifications on the diesel are this: 215 horsepower at 3800 rpm,376 lb-ft of torque at a low1600-2800 rpm, and a towing capacity rated at amaximum of 7,400 lbs. What these numbers don"t tell you is that whileracking up such impressive performance figures, the diesel producesapproximately 30-percent fewer C02 emissions than its gasoline-burningcounterparts.

While the above statistics help build a case for driving adiesel-powered Grand Cherokee, old perceptions die hard. The GC"s dieselis not a loud, stinking, soot belching beast. The engine is so refinedthat you"ll find this same V-6 under the hoods of Mercedes-Benz E-Classsedans and R-Class crossovers. In fact, the engine is so good that it ownsa spot on the respected Ward"s list of Ten Best Engines for 2008. http://wardsauto.com/reports/2008/tenbest/winners/daimler_dohc_turbodiesel/

One important reason for its inclusion is driveability. At idle, theengine is smooth. While there is some noise (you can hear the enginerunning), it"s nothing intrusive. Roll down the window, and the timber ofthe idle sounds a bit different from a gasoline V-6, but you"d nevermistake the sound for a UPS truck. But nobody buys a vehicle because ofhow its engine sounds or doesn"t sound (unless it"s totally objectionable);people care about how the vehicle drives. And the diesel-powered GrandCherokee drives very well.

The first thing you notice is its power off the line—it feelsunstoppable. The thrust is fluid. The gear changes from the 5-speedautomatic are smooth, and once on the highway, the transmission rarelyneeds to downshift because the engine produces so much torque. Theexperience is far superior to many V-6 powered SUVs that need to drop downa cog or two just to maintain a set speed when faced with something asminimal as a slight incline.

The Grand Cherokee"s 5-speed automatic transmission was a good but notperfect match for the diesel. Cruising upwards of 80 mph had the enginespinning over 3000 rpm (about normal for a V-6), but because of theengine"s robust torque, it seems that a sixth gear or a taller overdrivecould have increased fuel economy even more. Many of today"s SUVs areusing 6-speed automatic transmissions, so perhaps an upgrade is in theworks, especially since Mercedes-Benz offers the same engine with a 7-speedautomatic in their GL320i SUV.

We didn"t have an opportunity to drive the diesel off road, but itstorque characteristics seem like they would marry perfectly with rockhopping and trail riding. Both activities are low-speed and favor vehicleswith abundant torque.

Currently, the Grand Cherokee may be optioned with the diesel in 42states. Full 50-state certification for this engine is coming in 2009 withthe introduction of Bluetech exhaust gas treatment technology. Bluetech isa descriptor used by Mercedes-Benz to identify its cleanest-running dieselengines which will meet or exceed all pending exhaust emissions targets inthe US and European markets.

Even without Blutech, the 3.0-liter V-6 is among the cleanest runningdiesels around. We even gave the tailpipe a sniff while the Grand Cherokeeidled in the parking lot of our office, and there was no soot or the awfuleau de diesel that one might smell if you tried the same stunt with anolder diesel vehicle.

We did notice one curiosity with the diesel; unlike gasoline-powered GCsthat include information on instant economy, estimated range, and averagefuel economy, our diesel didn"t. Our thinking is that the Mercedes-Benzengine electronics aren"t compatible with the system existing in thecurrent Grand Cherokees. Perhaps they"ll get that sorted out for 2009.

Compared to what hybrids cost, upgrading to this diesel engine isrelatively cost effective. Optioning up to the diesel from the base3.7-liter V-6 runs $3,235. This compares to a similar engine option fromthe 3.7-liter V-6 to the 4.7-liter V-8 that costs $1,580, but doesn"t offera fuel economy increase or provide nearly the torque of the diesel.

The age of the diesel is dawning on the United States, and because ofvehicles like this Grand Cherokee, we should run out and enjoy each newday.

About the author: Rex Roy is a Detroit-based automotive enthusiast,journalist and author. His recently published coffee table book, MotorCity Dream Garages, is available at all major book sellers, Amazon.com, andon e-Bay.