2005 Tacoma

I don't presume to be an engine design engineer, so I would recommend that you use what it calls for in the manual. I assume that specific clearances in the engine require a specific lubricant for maximum efficiency and longevity.

Why do you want to change?

Because I live in South Florida and I've heard that since the weather is too calid (hot) it is better to put a different oil. The other time I used

The manual lists temp ranges for specific oil weights. There's a neat little chart in there.

It potentially can hurt the engine, but probably will not - they are making the internal clearances of the engines tighter to improve fuel efficiency, and when they specify using the lower viscosity motor oil that gets them another fraction of a MPH in Fleet Fuel Efficiency.

I wouldn't go up past a 5W30 or 10W30 without a really good reason.

If you are worried about the heat go to a full synthetic motor oil like Mobil-1, it handles low and high temperatures like nothing else.

-->--

My manual says to use 5W-30. It says you can use 10W-30 if that is all that is available, but to change it back to 5W-30 at the next oil change or as soon as available. So IMO 40weight oil is not recommended.