You guys are saying the same thing!
In theory 5W/30 is the same as straight 30 at hot temperatures but in reality it doesn't work that way.
Multi-grade oils are a compromise.
While the trend today is to run as thin as oil as possible to get another miniscule amount of mpg & hp, how does this really thin oil affect engine protection & longevity?
Especially in a high revving 4 cylinder engine?
In addition, today's modern "catalytic & environment friendly" engine oils are worse than ever.
I prefer thicker oils in my engines in the summer, running 10W-40 in our TSX and my 5.0L Mustang & 10W-30 in the TSX in the winter.
...Joe