Napa Gold=Wix my local Napa store has a half off filter day on every other Friday all Napa gold filters air,fuel and oil filters and as you know this can save some serious$$$ and as far as oil goes stick with Rotell 15-40 yes it's more money but well worth it in the long run

 

The shop book for a 99 K3500 6.5L states that the crankcase capacity with filter is 8.0 quarts.