Just got my trinity in today that was replaced. Question I have is what tune to use. I see a diablosport custom tune and a 91 Octane tune. What one is better? I thought it comes with a 93 octane tune? that is the gas I use here.

I have read from knowledgeabe sources that Rotella T6 synthetic motor oil https://bestarny.com/oils-for-duramax/ is the very best for my C223 engine. My question is, does using the synthetic oil extend the number of miles I can drive between oil changes or should I stick to the 3,000 mile interval ...