Engine got very hot.

[meimk]

Thick oil may well make it run hotter (very slightly) - more "work" for the engine just pumping that thicker oil. I understand you're in Florida and all, but by that chart - you honestly won't be using the cart under 68 degrees F?

[slonomo]

I think multi viscosity oils are best for areas that have big temp swings in the weather. Here in Ohio we see temps below 20 F in the winter and above 90 in the summer. I run Rotella 15w40 right now, since I have a bunch left over from owning two diesel pickups. But the Rotella oils are great they have higher zinc and phosphorus than a typical oil. I also like the synthetic version.

With that said, I don't think you will do any damage to your engine using 40 weight oil. The old rule of thumb used to be "heavier weights will protect better but not be as efficient" so you might see an increase in fuel usage, but probably marginal.

Most important with engine oil.....frequent changes! If you are religious with keeping clean oil in your engine you will have your best chance of the engine lasting as long as it possibly can.

Yes, heat can kill an engine. But those engines are designed to run in the climate you are running it in. Keep the engine in tip top running condition and change the oil often, don't abuse it, and it'll do just fine.