T S Traveller oil.

[DickWells]

On my third change, now, in my Sierra, and pretty happy with it. Traveller 15-40, from Tractor Supply. Lots of trepidation, before I tried it the first time, but I heard from our son and others that it was being used successfully, so I went for it. Seems to last as long, or longer than Castrol, before the first quart has to be added, and goes just as long before turning black.
I use Baldwin filters, exclusively, in my dual bypass Amsoil system, and just went 13,000 miles, pretty much inadvertently, before this change. Added 2, or three quarts in that time, which is just about average for this truck ever since I bought it in 06. Still costs close to 60 bucks for oil and filters, but it's a far cry from the $196 that it cost me for Amsoil the last time I went that way, back in 08. Never again! Tried it for two changes and it didn't net me any advantage at all.

[Kennedy]

I run Delvac 1 nearly exclusively here. Delvac 1300 would be my second choice.

$24+$24+$12 for $60 a change (oil cost only) and I dump every 10 k. I might have to add 1 qt in that time. With the recent rebate I stocked up and have enough oil for 200,000 miles of Dmax operation more or less at 1/2 price.

[DickWells]

I never have tried Delvac, John. Maybe I should have. I get my Baldwin filters on-line, and, IIRC, the Trav. oil cost me 40-some-odd dollars, and I buy 2 each of the 2 different filters, for two oil changes, at about the same price for 49 something, making it come close to your figures. I intend to change every 10K, but this last one sneaked up on me, with new filters in Brownsville, Texas at the time that I headed for Florida with around 8.5 on the old oil. Somehow, I put on almost a thousand miles just kicking around Port Charlotte for 3-4 weeks.