Jeep Grand Cherokee - preferred oil

[99]

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Originally posted by Gary Allan:

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Of course, the 4.0L engine is the tried and true I6 ('straight' six) that Jeep has used for years in the Cherokee and the Wrangler.

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And it was used by AMC in Gremlins, Hornets, and a variety of other vehicles. Very stout and totally reliable engine. Great torque, peaking at a very low rpm and flat throughout the useable rpm range. It's just too heavy and inefficient.

I knew that this engine was doomed. There's no place for it in todays (m)all terrain vehicles.

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I just read that the 2007 Wrangler will have the 3.7L V6 engine (from the Jeep Liberty) for the 'six option' and the 2.4L four cylinder (instead of the present 2.5 L four). I wonder if this 2.4 L is the same four Chrysler-Jeep uses in their Neon.

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The 2.5 was discontinued in the 03 Jeep model line. The 2.4 is the same engine that you see in the NEON. It isn't any more economical ..but has better performance and much higher hp capability with its 4 valve cross flow DOHC design. It has Euro DNA in it.

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The 4.0 is dead. The writing's been on the wall for a few years now and DC has pulled the plug on it. I don't like their decision, but they have their plans for the Jeep brand and they're going to do what they want. As it is now, the 4.0 barely passes emissions requirements, NVH requirements and fuel economy regs and I believe upcoming misfire requirements weren't going to work with the 4.0 block. As it is now the 4.0 is only used in the Wrangler...no other Jeeps use the I6 so that should tell you something right there. The 4.0 used to be Jeep's flagship engine. It's really a dinosaur of an engine by today's whiz-bang standards. DC could've put a aluminum SOHC or DOHC crossflow head on it and did fuel injection/engine control improvements, cast a new block in aluminum, etc, to bring it up to date, but I doubt they could have justified it to the bean counters.

There's talk of using a new 4.0 V6 to replace the 4.0 I6, but I think that's just playing the number game to keep the 4.0 purists happy to a point. Do a Google search on the TK or 07 Wrangler and you'll find tons on info on this upcoming Jeep. Lots of very recent spy shots on models that seem like they are ready for production. I can't wait to get my hands on one.

The 2.4 is EONs ahead of the old boat anchor 2.5. I've driven a SE with the 2.4 and it's so good there's not much seat of the pants difference between it and a 4.0 model anymore. At least not like there was with the 2.5. The 2.5 was WAY overdue for a replacement ever since the TJ came out. Yes it is the same engine as in the Neon, better yet, it's the same engine minus the turbo as the SRT Neon and the turbo PT Cruiser. Mopar Performance has a ton of parts for the 2.4, so if you want to make more power than your Jeep can handle, they have it.

[ September 21, 2005, 02:43 PM: Message edited by: 99 ]

 

[bobo]

Unfortunately, my thread has been whored to death!

 

[wrangler]

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Unfortunately, my thread has been whored to death!

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[bobo]

Well at least you have a sense of humor, wrangler, lol!

 

[MarkC]

"The 4.0 is dead. The writing's been on the wall for a few years now and DC has pulled the plug on it. I don't like their decision, but they have their plans for the Jeep brand and they're going to do what they want. As it is now, the 4.0 barely passes emissions requirements,"

Ha! The one under the hood of my Cherokee certainly isn't dead, and doesn't appear to be thinking about ending its career anytime soon. And, at least in Washington it passes emissions tests with flying colors. I dread the day when I will have to replace it with a V-6, or anything else.

 

[Gary Allan]

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Of course, the 4.0L engine is the tried and true I6 ('straight' six) that Jeep has used for years in the Cherokee and the Wrangler.

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And it was used by AMC in Gremlins, Hornets, and a variety of other vehicles. Very stout and totally reliable engine. Great torque, peaking at a very low rpm and flat throughout the useable rpm range. It's just too heavy and inefficient.

I knew that this engine was doomed. There's no place for it in todays (m)all terrain vehicles.

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I just read that the 2007 Wrangler will have the 3.7L V6 engine (from the Jeep Liberty) for the 'six option' and the 2.4L four cylinder (instead of the present 2.5 L four). I wonder if this 2.4 L is the same four Chrysler-Jeep uses in their Neon.

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The 2.5 was discontinued in the 03 Jeep model line. The 2.4 is the same engine that you see in the NEON. It isn't any more economical ..but has better performance and much higher hp capability with its 4 valve cross flow DOHC design. It has Euro DNA in it.

 

[XS650]

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Originally posted by 99:

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Originally posted by XS650:

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Originally posted by Eddie:
A truly great old engine. A mil-spec engine that will take abuse unlike any alumanum engine and that is why the military chose it.

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Where is the military using it?

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Overseas, but it isn't the US military though. I believe some country in the Middle East has been using our Jeep Wranglers for years now.

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That wouldn't exactly make it a mil-spec engine.

 

[Zaedock]

[/qb][/QUOTE]

The 2.4 is EONs ahead of the old boat anchor 2.5. I've driven a SE with the 2.4 and it's so good there's not much seat of the pants difference between it and a 4.0 model anymore. At least not like there was with the 2.5. The 2.5 was WAY overdue for a replacement ever since the TJ came out. Yes it is the same engine as in the Neon, better yet, it's the same engine minus the turbo as the SRT Neon and the turbo PT Cruiser. Mopar Performance has a ton of parts for the 2.4, so if you want to make more power than your Jeep can handle, they have it. [/QB][/QUOTE]

You're comparing an engine designed for a car (the 2.4L) vs, an engine that AMC purposely designed for a truck. The 2.5L has a larger bore and makes it's torque 800 RPM lower. Sure, the 2.4L probably does "feel" better on the street, but what's it feel like lugging on the trail?

The 3.7LV6 and 4.0LI6 aren't even in the same realm. The 3.7 makes it's peak torque around 4000RPM. The 4.0L's flat torque curve comes on at 1800RPM. They both have 235 lb/ft. Which one is better? IMO not the 3.7L. The mileage difference is negligable too. The only reason DC built the 3.7L is because it is smaller and weighs less. They are conforming to gov regs and soccer Mom's who want a smoother running engine that goes better on the highway. Same goes for the 2.4L.
(I won't even get into the Liberty's IFS...) The 2.5L has been around, virtually unchanged, for 20 years. The 4.0L 18 years. They are the last of the "real" Jeep engines that were made to go places that soccer Mom's weren't.
The seat of the pants feeling comes on around 1/2 MPH and stops when the seatbelt tensioner releases...

P.S. The 4.0L was never used in a Gremlin or Hornet. That was the 258 (4.2L). While similar, the 4.0L's head design is actually taken from the 2.5L "TRUCK" engine.

 

[Eddie]

The US military did request that a 6 cyl engine be built for light trucks and jeep type vehicles. Two I6 engine were submitted for testing. The two engine were the 4.0L I6 used by Jeep and were tested with an iron pushrod version AND an aluminum OHC version. The milatary chose the pushrod version with iron block & heads as the most robust (read able to take abuse) and more familiar to the Military mechanics (pushrods). I read this articule that was written up years ago in "Automotive Industries" I seem to remember. The 4.0L I6 engine was indeed a true Mil-spec engine.

 

[XS650]

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Originally posted by Eddie:
The US military did request that a 6 cyl engine be built for light trucks and jeep type vehicles. Two I6 engine were submitted for testing. The two engine were the 4.0L I6 used by Jeep and were tested with an iron pushrod version AND an aluminum OHC version. The milatary chose the pushrod version with iron block & heads as the most robust (read able to take abuse) and more familiar to the Military mechanics (pushrods). I read this articule that was written up years ago in "Automotive Industries" I seem to remember. The 4.0L I6 engine was indeed a true Mil-spec engine.

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Do you have better source? The OHC version was used in a lot of varients of Kaiser built US Army vehicles like the M-715, but right off hand I can't think of any that used the push-rod version. Which ones used the pushrod engine?

If you have the actual Mil Spec number I might be able to look it up.