What oil would you recommend (ctxt!)

[FrayAdjacent]

I'm going to be changing the oil in my recently aquired 2001 Boxster. I have no idea when the oil was last changed, and since I'm doing and have done a lot of periodic maintenance, I might as well do the oil!

I will be using Mobile One Synthetic, for sure, but I'm not sure which weight will be best.

GIVEN:

- My daily commute is short, the engine will be up to operating temperature within a mile of destination
- I drive few enough miles that I likely won't be changing it again for 12 months
- It gets HOT here in Texas in the summer
- It doesn't usually get below freezing for long in the winter

In you guys' opinions, would it be better to use a 10W40, or 15W50? I think the 40 weight, so that it will flow better in my short trips, where the engine is barely up to operating temperature by the time I get to work (or get home)... but I'm thinking the 50 weight, because it gets HOT here in the summer.

Would 50 weight be OK given that we rarely ever get below freezing here? We DO have weather below 50 degrees quite a bit, but lower than 40 is much more rare.

I appreciate your experienced input.