Originally Posted by SouthArk370Z

You're making too many assumptions and worrying needlessly.

Very few dealers are that picky about the oil change interval. I don't put a lot of miles on my car (<18k miles on an '09) and often go four to four-and-a-half months between changes. Nobody has said a word about it when I've had warranty work done. (But I've never needed a new engine/trans/diff.)

As mentioned earlier, the dealer cannot require you to get your oil changes done there. All you need is receipts showing that you purchased/installed the proper oil and filter.

As others have pointed out, the dealer can't reject a warranty claim on a body part just because you haven't taken care of the drivetrain (and vice versa).

Your warranty is with Nissan, not the dealer. If you don't like the way the dealer painted the shop bays, you can go to another dealer and get your warranty work done.