Couple questions.
First, I have the 2004 Cummins HO in my 2500 Dodge quad cab. I plan on using the fleetguard filter and amsoil 15-40 following the break in period of 15000 to 20000 miles. Currently using valvoline per dealer installation. How many miles are you guys traveling before oil changes using synthetic oil?

Second question, the maintenance says to change the rear end oil every 15000 miles. I looked under and can't find a drain plug, only a fill plug. Is the lower bolt on the housing going to drain the gear box by removal, or must I remove all bolts and then replace gasket of cover once removed for draining.

Thanks for all the input in past and now.
Dauntless