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.