Rotella T6 in my 7.3 and all my ATV's and mower/snowblower. It's easier to come by plus has the JASO certifications for wet clutch/shared engine and transmission use in my ATV's. I don't know of any other HDEO that has those certs.
Delo here currently.
Started using 15w30 SD in my 6.0, I have continued using it in my 6.7 .
But I've run them all, Mobil Delsmack, Valveater Premium Blue, Shell Rosmella, SuperTech, and even Harvest King.
In the conventional 15w40's there really is very little difference in wear rates and overall performance with any of them.
So, what do you guys with diesel vehicles run? ...
Typically I'll run the least expensive of any API approved HDEO I can find at the time. Might be a SOPUS product on a sales push, or Devlac on rebate, or Peak on a closeout, or ... whatever.
Right now my stash is VPB semi-syn 10w-30 because it was the cheapest at the time to stock up my shelf.
I have run T6 rotella in a jeep for the last 100 plus thousand miles. But walmart had the Delo semi synth 10w30 on clearance for 19 bucks for a 2.5 gallon jug. I bought 4 jugs. I have it in one of my silverados and about to run it in my lawn mower.
I swear by Delo myself. But T4/T5/T6 is good also. I Just did a lot of reading and honestly Chevron is always innovating oil production in past so I give them my hard earned money. Delo is also always available easily in my area so I tend to favor them. T6 is little hard to come by.
Been running delo 400LE 15w-40 for a couple years with great OA. Was available at the local walmart for awhile, but since they switched to CK-4 the CJ-4 stuff is all gone. I stocked up for a couple OCI, but will need to decide if I start ordering delo or switch to another oil.
I'm seeing amazing results with Delo's CK-4 oil. But I believe any CK-4 oil (including store brands) are the way to go. In my OTR truck, it's living up to the hype that the oil industry had promoted.
I think any of the newest HDEOs would net me great results in my truck. I just happen to get oil changes for an amazing price through the carrier that I do business with and they use Delo products in every application.
It is interesting that Castrol makes a 15w40, but hardly anybody sells it and I don't know of anyone who has used it. How can all their other oils be so common, yet their HDEO is practically unknown?
I used Castrol Hypuron (semi-syn) for a few years (2005-2009 I guess). I got it at Fleet Pride (nationwide heavy duty parts stores) for a very reasonable cost in 5 gallon buckets. I would guess that they still sell it, but I think Castrol changed the name to Vecton (???).
It did a great job. I used it with an FS-2500 bypass filter and worked my way to 60k mile intervals in my C15 Cats.
When I got my diesel truck last year, the first oil change I did was with Delo 400 LE synthetic 5W-40. This year, I used Rotella T6 5W-40. Both are excellent oils, as are almost all the HDEOs. I picked the oils based on price at the time.