When I bought my 92 3/4 ton turbo diesel, the dealer offered free oil changes for life. I asked what oil they provided.
The service manager said they use Quaker State 30 weight.
I sometimes let them change it but provided my own oil.
When I upgraded to the 94 2500, I didn't even bother with them.
I change all the fluids and filters myself and will continue to do so.
No problem getting rid of the used oils. A local truck repair shop burns it in their shop heater and will take all I can give them.