K. I know this experience should be opposite but here it goes.
I bought my charger this summer. I established a mpg baseline using M1 5w-20. My oil temps on the highway at their lowest was 213f at 70mph. I established my baseline mpg's averaged over 3000 miles.
Just to comment on oil condition it wasn't yet blackened however I had just got the car so I was high rpm driving for a lot of the interval and I saw oil temps as high as 265f and I decided that was my cut-off temp and quit driving hard once that temp was reached. I got the oil that hot on a daily basis over 3000 miles.
So I drained the oil,changed the filter and used an identical filter and oil except this time I added mos2.
I ran the mos2 additized oil for over 5000 miles. I noticed that the oil temps dropped to 213f steady cruising at 70mph and I found that it took much longer for the oil to reach the 265f oil temp cut-off point,which pleased me because I could play harder,longer.
So I drained that oil fill and I had liqui-moly 0w-40 in stock so I used it with a quart of pp 0w-20 I had in stock and added a can of liqui-moly cera-tec.
Immediately my 70mph cruising oil temp dropped to 200 and maintained that temp. And when I beat on it I found it very difficult to attain my 265f oil temp cut-off point. I could only heat it up to that temp if I drove highway speeds in second gear for 15-20 minutes.
Ambient temps have no bearing on my oil temps. It was -26c here last week and when I drove I to the city my oil temps maxxed at 200f at 70mph and when I first changed the oil and added cera-tec our ambient temps were still 15-20 degrees Celsius.
So to conclude straight oil ran at 220f at 70mph
Mos2 treated 5w-20 ran at 210-213f at 70mph
Cera-tec treated 0w-40 with 1/6th 0w-20 ran at 200f
In all the literature I've read about oil I learned that thinner oil dissipates heat faster,so I took that to mean lower oil temps as the grade decreases which I confirmed on my Harley when going from motul 10w-60 to rotella 15w-40.
My I/R temp gun displayed a 12f oil temp reduction and my dipstick thermometer displayed a bit more than a 15f temp reduction going from a 10w-60 ester based bike oil to a conventional 15w-40 hdeo,so I was mystified as to how my charger's oil temp decreased even though I went 2 grades thicker.
I have to assume the additives reduced the oil temps because they reduced the friction in the rotating assembly of my hemi.
It's the only explanation because after the first oil change the only difference was mos2 and the second change should have actually gotten hotter oil temps yet they dropped another 10 degrees.
Cera-tec isn't cheap but go the the liqui-moly site. It's some seriously high tech stuff. Mos2 is much cheaper and easy to find. Napa carries it.
After reading the posts from previous owners I think in this application it may be the prudent to buy the best oil you can find,regardless of cost.
However I am still cheap so if I was in your shoes I'd run devlac elite 0w-30 or the 0w-40,then the M1 0w-40 and redline 0w-30 and have each one analyzed then make a decision based on the data acquired.
Then you can establish drain intervals and factor in cost and see which is the most cost effective while still providing the best protection available.
OP. It's already been mentioned that some owners already use an hdeo so it's not uncharted territory however I'd lean towards a 0w simply because at all temps the oil will flow faster and not completely peg oil pressure,lowering the possibility of the filter going into bypass.
Just thought I'd share my experiences. I find that real experience is far more valuable than opinions based on a guess at best(I expect to be flamed since there are a few members whom insist these additives do nothing even though there are countless threads where members praise these products,so don't listen to people who've never even used the stuff)
Flame away