Heath,
I am doing the Bypass kit on my 6.0L. I live in Cali and it is around 60-70 all year round I was wondering what oil I should use. Also i am going to be moving to WY and it is a lot hotter in the summer and cold in the winter what would be a good oil for there? Also how long could i go on a oil change. Thanks Bud

 

Those 6.0L's are tough on oil from what I've seen. Many 40 weights have been shearing down to 30. I see a lot of 6.0 owners just using a 10/30 or a 5/30 year round. Our 5/30 diesel oil is a very good one. Heavy additive package and our most expensive. If it were me and I was installing the bypass for longer intervals, that would be my oil of choice.
As for intervals, you can go 15k without testing it, but beyond that you have to keep an eye on it. I've seen the oil go 30k+ but every truck and condition is different. I would send a sample at 15k. If ok, I'd go to 25, 35, etc. and test each time.
The full flow filter is good for 15k, but you can change the bypass filter every other time if you wish. I do both but that's just me.
If you'd like pricing on the kit, just let me know.