I change my oil and fuel filter every 5-6,000 miles. I use 10 quarts of Delo 400. I buy three gallons at a time in a box from Costco, and usually purchase my Baldwin oil filter and Parker fuel filter only from Performance Truck Products. He's on this forum, or you can go to their website. Also, there is a bunch of great dealers on here, i just have personally used PTP so that's why i would recommended them. Again, I use Delo, its not a synthetic, just a great heavy duty motor oil that we use in our big trucks so I can't see why it wouldn't be good enough for my pickup. You can get as crazy as you want with oils and synthetics, as for "dealership" oil, I couldn't tell you what it is, I'm sure its something like Delo 400. Hope this helps.
2005 Chevy 2500HD Crewcab 4x4 LLY; 4" MBRP Turbo back; 06 LBZ Mouthpiece and airbox with intake resonator plugged; Predator Programmer set for 45hp 100ft/lbs (tow); ISSPRO Pyro/Boost pillar gauges
B&W turnover ball; Torsion keys and shock extenders-leveled; 285/75/16 BFG All-Terrains
"War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse. The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." -John Stuart Mill