You don't HAVE to continue running diesel engine oil. You can run anything you want. It is said that the high zinc content in diesel engine oils, while great for engines in general, eventually kills the catalytic converters that gasoline engines have. Some say that's not true, others say it's true but will take a really long time. I ran gasoline engine full synthetic oil (Pennzoil Platinum) until recently when I removed the cats. I switched to Rotella in the T6 flavor cuz I'll only run full synthetic. There is now a Rotella formulated for gasoline engines that appears to be an excellent oil. Since you asked specifically about Rotella, I'd say the one that's best for your '07 is the new one for gasoline engines. If some of that work that the previous owner did was removing the cats, then you can still run that gas engine Rotella or the continue with the diesel engine Rotella, again, in full synthetic.
Bottoms up!
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