Vic Dura wrote:
I just bought a new car last month. My previous car was a 1997 model
and it specified 10w-40 motor oil, as had every car I have owned for
the past 30 years. This new car (a 2005 Ford Focus) specifies 5w-20
oil. I've since found out that 5w-20 has been pretty much standard for
the past couple of years.

Question: Why the apparent reduction in lubricating requirements? I
can understand that theoretically the 5w requires less power to pump
and therefor *might* result in some mileage improvement; but the high
temp reduction from 40 equivalent to 20 equivalent doesn't make sense
to me.

What am I missing?

thinner the oil, better the gas mileage, I believe