The 3.5L seems to me to be a very capable motor for what it was designed to do - be the V6 workhorse for an entire company for a decade or so. However, some of the design decisions made by the engineers are curious to say the least, and destined to cause issues toward the end of the parts' service life to say the most.
But like you say, it was a long time ago when they were designing these puppies, so I will admit my second-guessing of certain things amounts to little more than armchair quarterbacking on Tuesday morning...several years down the road, that is.
Still, whoever was in charge of deciding upon, or giving the final approval over, the stock tune that would be installed and run on the 3.5Ls leaving the factory should be put on trial for crimes against humanity...well, maybe not crimes against humanity, more like crimes against innocent automotive enthusiasts who's only desire is to enjoy the driving experience their vehicle has to offer.
I've been running a modified version of the 93 octane canned tune that comes with the DS Predators for about 4ish months now (~15K of the 20K miles I've put on it so far), and I can honestly say I will never go back to the stock tune on that car! Its stock tune from the factory made for an absolutely disappointing driving experience...just abysmal!
But let's not forget to give credit where credit is due in all of this. I don't know if the Chargers are as overweight as the Challengers (I have a sneaking suspicion they are), but the Challengers are friggin' tuna boats, and trying to move one around with a factory tuned 3.5L (+A5+2.87, etc.) is just not a scenario that was ever going to result in anything but abject failure, IMHO.
But I digest...
This thread is about MPGs, so I will end this diatribe with a quick fuel mileage anecdote: I filled up on 93 octane last night, and the total amount I paid for the 15ish gallons of gas was $30 and some change. Gas is stunningly cheap right now, and since I have to use the premium grade stuff, these prices are making me happier'n a pig in sh*t every time I go fill up. As such, I have been slack about tracking my MPGs lately, I forgot to write the miles down the last two times. Chalk it up to sticker shock I guess...I was so shocked at how little I was paying, I forgot to record the miles to figure MPGs!
It's probably for the best though, I suspect they have gone down a few MPGs recently. I have been chasing some rather elusive ST KR in my WOT data logs, and so I keep having to do more and more WOT driving to check if my changes are working, and so on...
It's a sacrifice sure, but I want to do everything I can to further science you know...