Guy who posted this was an engineer for FCA on the Pentastar team. His comments about start/stop are eye opening:
“As for the other comment yes, without a doubt turning off ESS will significantly reduce engine wear in the 3.6. I dealt directly with the data on that. I'll keep my comments to my limited experience but other engines are no different and will follow suit. Noted above was the need for iROX bearing coatings, these were entirely driven by ESS operating issues and VERY high engine wear. They provided a lower coefficient of friction (thus reduced wear) as the crankshaft made contact with the bearings (Fun fact: the front and rear bearings will have the most wear because of the accessory drive loading and trans loading). The problem is simple. A hydrodynamic bearing doesn't touch any other metal, it's just floating on oil. So when you stop the engine its like killing the throttle pulling a skier in a boat. The skier no longer is on top of the water and sinks, scraping the sandbar and wearing the down the ski. The engine is doing the same to itself every time ESS goes off. Crankshaft, cams, timing chains all go to zero velocity and grind against their metal neighbor. E85 is another animal. it basically washes out the oil that is embedded in the cross hatching which is intended to actually hold oil. Also all other peaks and valleys of machined parts (nothing is actually smooth!) like the cams, timing chain etc. When you combined with ESS and E85 you are basically scraping metal on metal for a very high percentage of the engine life vs. a gasoline steady state cycle. It was so high the cylinder bores on our general durability runs with ESS were mirror smooth by the end. Very interesting stuff. I wont run ESS or E85 for the record. lol”
Originally Posted by OIL_UDDERNice! As an former Pentastar design engineer I am slightly bias but the engine is really high quality. Few points from the development using tens of millions of dollars in analysis and testing regarding the oil and durability..... The lighter oil was chosen mostly...
www.bobistheoilguy.com
First, V6 engines are notably problematic for MDS, as described here:
"Bob Sheaves on why the system is usually used on V8 engines, not V6 engines:
An Otto cycle engine takes two revolutions [full turns] of the crankshaft to fire all the cylinders. Two revolutions times 360 degrees [one complete circle] equals 720 degrees of rotation; dividing that by the number of cylinders gives you 120 degrees [on a V6], so you have a cylinder firing every 120 degrees of rotation. On a V6, when you take out half of the cylinders, you have increased the firing rotation to 240 degrees (720/3), balanced between each firing of a cylinder but with increased harmonic vibrations as the revolutions per minute increase. Deactivation of two or four cylinders in a V6 would mean losing the multiple of six cylinders, which is what keeps the engine in primary balance. [Honda deactivates two cylinders on its V6 engine, which improves the balance by making the firing rotation 180°, the same as in a V8 firing on half its cylinders. With all eight cylinders firing, V8 engines fire every 90 degrees.]"
So you might question the author of the quote above on their comments about how "...it really is no different", especially when they admitted to having limited experience in this area. Meanwhile, on the HEMI:
"Chrysler engineer Cole added:
The modern Hemi always shuts off the same four cylinders. In our durability test cycle (150,000 customer equivalent miles driven at the 95th percentile, meaning that only 5% of our owners are more abusive than our testing), we have not found any adverse wear patterns.”
(Both of the above statements were
sourced from Allpar.)
Back in 2004, Chrysler wrote in a special report on the HEMI, "...MDS was part of the engine's original design. This resulted in a cylinder-deactivation system that is elegantly simple and completely integrated into the engine design. The benefits are fewer parts, maximum reliability and lower cost...
The HEMI engine with MDS has completed over 6.5 million customer-equivalent miles through Chrysler Group's development and durability testing... The system deactivates the valve lifters. This keeps the valves in four cylinders closed, and there is no combustion. In addition to stopping combustion, energy is not lost by pumping air through these cylinders... Improved fuel economy is realized without any change in customer experience — drivers will receive the benefit without changing their driving habits and without compromising style, comfort or convenience."
Draw your own conclusions, of course, but these "modern HEMI" engines have proven to be pretty reliable over the past 15+ years and >3 million units.