The image below shows the specs from my engine manual (above) and from the Rotella T6 synthetic oil I just bought. I assume that the synthetic oil is better, but the specs don't match up. I don't want to assume wrong.

Also, I bought SAE 5w-40 but the manual only discusses 15w40 for wide temperature range operation. Also, the engine manual has a chart showing that 15w-40 is rated to run at ambient temps well above 110F (same as straight 30 or 40-weight, but the straight-weight isn't suitable for colder temps). Anyone know of an issue running 5W-40 in the summer?