So what weight Mobil 1 are people running?

15/50
0-40
10-30 High Mileage
10w-40 High Mileage

What is best for hot summer temperatures?

What is best for long driving during the hot temperatures?

So far I am hearing 15/50 from the forum. Am I getting this wrong?
The 10W-40 seems also like a strong number 1 contender as being the
1st weight choice.

What is the difference really between 15/50 and 10/40?

Robert
NY