I'm about to fill my gearbox and transfer case with ATF oil. I want to know what is best suited for it. The automatic gearbox has been worked on for heavy duty quick shifting, therefore I want very good quality oil in it as I intend to drive it hard. I was planning on using Penrite ATF Synthetic, which is a full synthetic oil. It meets Mercon-V and Dexron III standards. I've spoken to Nissan and they recommend D Matic which is also a full synthetic oil. Which one is better, the OEM oil or aftermarket performance oil? Or they they just as equally good as each other. I did notice though that the D Matic was slightly more expensive but Nissan products usually are and their quality isn't always worth the markup they put on. Any feedback would be appreciated.