Well, I bought a 3.7L......... - Jeep Commander Forums: Jeep Commander Forum
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post #1 of 9 (permalink) Old 04-30-2016, 07:55 AM Thread Starter
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Well, I bought a 3.7L.........

I know the V8's are the preferred choice but couldn't turn down a 2010 Sport with quite a few limited trim upgrades and 65K miles for 15K. What do need to be looking for with the 3.7 in potential trouble issues besides crappy gas mileage. Thanks in advance!
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post #2 of 9 (permalink) Old 04-30-2016, 03:56 PM
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Join Date: Oct 2015
Location: East Coast of Florida; Proud to have served.
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I had a 2008 Jeep Grand Cherokee Laredo Rocky Mountain Edition with the 3.7L V-6 and QuadraTrac 1 4WD before I bought the Commander I have now - and the Grand Cherokee was obviously smaller & lighter than a Commander.

I had bought the V-6 because I thought I would get better gas mileage - which obviously turned out not to be the case. I probably should have done some homework on the Jeep enigines before I bought it. To be completely truthful, if I knew then what I know now, about the current line of Jeep Engines, I would not have bought the 3.7L V-6.

However, all in all, it was a solid running engine for the 3 yrs I had it but I am here to tell you, your Commander will probably be grossly under-powered, just like my Grand Cherokee was.

210 hp & 235 ft lbs of torque just doesn't cut it for a vehicle the size and weight of a Commander in my opinion.

Other then the lack of power, torque & gas mileage, I can't really say I had any issues with the engine.

All that being said, best of luck with your new Commander. Keep up with your basic maintenance & oil changes and you should be fine.


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Last edited by Big Blue; 05-01-2016 at 02:40 AM.
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post #3 of 9 (permalink) Old 05-01-2016, 11:50 AM
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The Commander is NOT the only vehicle that has almost no difference in mileage between the V6 and V8 option, its more and more common today.

Crash protection standards make the vehicles much heavier. Emissions standards reduce engine efficiency. Cafe standards force the designers to develop the engines to be as efficient as possible while still meeting emissions standards that take a huge bit out of the efficiency that could be possible.

What it comes down to, it takes a certain amount of energy to move the vehicle, all three engine options have the same efficiency and thus will consume the same amount of gasoline to output the energy. The HEMI with MDS, its even possible under certain conditions for it to be even more efficient that the V6, to result in better mileage in some cases. Again, you'd spend a lot more money for the much more expensive engine.

The 4.7L V8 and 3.7L V6 are the same engine, the V6 just has 2 cylinders chopped off. Actually the differences do require enough minor changes to each part that the parts are far less interchangeable than you would imagine, but you can tell every part started from the same design.

The only problem I have had with my 2010 V6 Commander (140k miles) has been an evaporative emissions fault, AC evaporator leak, and re-occuring #2 cylinder misfire.

The #2 cylinder misfire is the only one that relates to the 3.7L itself, it started at high miles, like 110k. It progressively got worse as I trouble shot it to try to figure out the root cause. I finally found it, it was the seals in the intake manifold allowing air to leak into the #2 intake port, creating a very lean A/F ratio for that cylinder. I replaced the seals on the intake manifold, much harder than most vehicle on the Commander, because even the V6 is such a tight fit, you have to remove a lot of additional things to get the intake manifold out.

The root of the problem is the plastic intake manifolds. So the V8's have the problem also, just as many of the have plastic intake manifolds as V6's. The plastic does have big advantages, but its softer and less rigid than metal, meaning it can NOT be clamped down as hard metal. So plastic intakes have a different kind of seals/gaskets to seal properly, more like an O-ring or Donut gasket, one for each port actually. These gasket seem to wear out, crush down and NOT spring back to keep the original seals over time and use and can start to leak. I have seen a lot of internet accounts of folks replacing these gaskets on their V8's, HEMI's and V6's at high miles. So it does seem to be a thing. After replacing my seals, remember I was at 140k miles, NOT only did it solve my #2 misfire issue, the engine ran much smoother and I got better mileage.

One more point on the plastic intake manifold seals. It was a lot of work to get the intake manifold out of the Commander, simple because you had to remove a lot, and even pull an engine mount bolt to lower the engine, just to make the room to lift and pull the intake manifold out. After doing the job I realized, you could easily cut the job in half if wanted. Since the gaskets are more like O-rings, they leave behind fairly clean surfaces, you really just need to scrub them down with a clean rag. So, you could avoid removing all the extra pieces to get the manifold out, simply by lifting the manifold on one side, pulling the seals and scrubbing down the surfaces with a clean rag and putting in the new seals, repeat for the other side and then torque down the manifold.

The chain driven camshafts, the chains should last the life of the engine. I've seen some speculation and results, that if you're really abusive to the engine, that results in a combination of poor lubrication with extreme loads and high rpms, the timing chains will likely be the first to go as the engine hits its worn out point.

Last edited by Mongo; 05-01-2016 at 01:42 PM.
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post #4 of 9 (permalink) Old 05-02-2016, 12:33 PM
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We had a Liberty with the 3.7 for 10 years and the only issued we had was oil consumption. A quart around every 2000 miles. It was adequately powered for the Liberty but I wouldn't wand one in my Commander.
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post #5 of 9 (permalink) Old 06-02-2016, 11:18 AM
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My 3.7 was getting 17-18mpg around town which I didn't think was too bad, before I got larger tires, now I see 16-17mpg. Does not seem to pick up too much on the highway, probably get a couple more mpg.
Definitely feels under-powered.

Curious what the rough average mpg a 4.7" gets?

Great info Mongo.
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post #6 of 9 (permalink) Old 06-02-2016, 01:55 PM
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I was getting 13mpg in town before I replaced the intake manifold seals and got new upstream O2 sensors. Now I get 14.5mpg in town.


My in town driving has heavy traffic and lots of lights, I'm a little heavy on the gas pedal as well.


17-18mpg is very good. I suspect your in town driving conditions are less lights and traffic than most and you've been driving very patiently to get that mileage.


I just got 18.5mpg last night on a somewhat highway drive of 80 miles, still heavy traffic and lights on the road, including going through several town where it turns into in town driving for a few miles. I have seen 20-22mpg on highway trips, on true highways holding a stead speed.
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post #7 of 9 (permalink) Old 06-03-2016, 07:04 AM
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The larger and apparently heavier tires really seem to bring down the mileage, after some more driving my 3.7L is closer to 15 in town. With the stock wheels and walmart grade tires I was a solid 17 close to 18.
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post #8 of 9 (permalink) Old 06-03-2016, 08:44 AM
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Hmmm, I do have BF Goodrich Rugged Terrain tires in the OEM size. They are heavier than the OEM tire. (They've been good all around tires, on-off road and lasting almost as long as the OEM, BTW).

Rotational inertia takes more energy than linear inertia to overcome. That means more weight in the body of the car, takes more energy to accelerate up to speed, but more weight in the wheels/tires takes exponentially more energy to spin up to speed.

But a couple pound difference in tires, just like an extra passenger really doesn't make much of a difference.

Now the overall tire diameter, changes the apparent gear ratios. Thus changes the rpm the engine operates at certain speeds. Those gear ratios were carefully selected to provide the best balance of power and economy.

So yes, if you select an over-sized tire, it should NOT be surprising if it has a huge impact on the MPG. As well, over-sized tires with custom wheels are often more than a couple pound difference in weight also subtracting from the power/economy.
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post #9 of 9 (permalink) Old 06-03-2016, 11:18 AM
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3.7 is a decent engine overall. Just keep the oil changed regularly, previous owner of ours didn't so we have a 2006 commander with a 2012 engine now. Even gunked up from neglect the 3.7 ran strong and had good compression. If the oil pick up had not become blocked we might still be on the original engine.

There may be a power difference vs a v8 but I am not put off the commander with the 3.7. I have a underpowered Cherokee that can not get out of its own way, and can forget about passing on the freeway if it eventually gets to speed, with this as my baseline for slow the commander v6 certainly has enough pick up and speed for the size of the jeep and its engine.


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