So yes you should go with full synthetic, with modern specs there are a ton of oils that are just as good as popular name brand oils. Kirkland, Supertech, amazon basics, box havoline, etc. Now these oils are dirt cheap, but because of the GF-6 specs they all look the same on the stat sheet. look at viscosity index, noack, hths, moly level, zinc levels, and operating visc. Boron and moly important additives tend to vary, good to find higher levels. There has been a movement of good base oils into this cheaper market, check pqia voa's and you will see. At a minimum you should get a cheap synthetic, one could say they are as good as anything and wont be wrong.
Now, if it gets cold in Kansas as in anywhere near 0f, then you consider 0 winter rated oils, this is where you can find varying qualities and specs. The stay in grade specs usually hint at pao base oils or very stable additive packages, these are merc, porsche, dexos, etc. Look on spec sheet. M1 is always a safe choice in 0 winter rated oils.
Pennzoils are what fca wants you to run, the most popular oil on the board. Clean base oils, but not really known for stay in grade, why? Because stay in grade is something fca didn't pursue in any of their ram specs. 5w20 is incredible stable, and for the HD they went semi thick to avoid even thinking about grade. Pennzoils do offer something just a tad different with the clean base oils and high detergent PUP, and are worth considering. However, you now have a high mileage engine, anything over 75k miles, and I would tend to think Pennzoil Platinum High Mileage would be a good choice for you if you can find it. Clean base oils, paired with great moly level, and the conditioners and detergency for a high mileage truck could be justification to spend a little more then the cheaper oils I had stated earlier, personal choice that's it.
If you wanted to dress up any oil to help with known hemi weaknesses, consider lubegard biotech, all it does is boost beneficial additives such as moly and phos. This can help prevent hemi tick and cam wear. Much white paper has been posted, and the moly in biotech is the correct type, there are many types.
If you get hemi tick at start up or warm idle tick, redline has proven to fix this issue backed with much science, long story trust me. 5w30 redline for trucks in warm places, 0w30 or lighter for trucks in cold places. But, no real reason to go this way unless you have hemi tick imo at this point. Kirkland or similar with 10 ounces biotech would be a great start, and is like 4 times cheaper then redline. If you want butter smooth engine, redline 5w30 will get you there, but a pretty penny for sure.
Now, just as important is filter, trust me and use a spun microglass filter, royal purple 20-820, wix xp, amsoil ea, fram ultra are all good choices. Read the oil filter thread for more info. Unless you change your oil every 3 mos, you NEED spun microglass imo. Many of us cut open filters for years on this issue.
study on moly and cam wear, look at the graphs here and see why the forum is high on lubegard biotech. It is oil soluble moly, the kind you want, and fca realizes the value in this as their hemi specific oil is loaded with moly. good day, hope this helps.
