I switched to the Mobil 1 0w-40 two changes ago and very happy I did even in the summer start up is even quicker, chain noise less than a second. Since in Europe this what they recommend for the Duratec. As long as Autozone gets enough volume they will continue to carry it.
The old school thought from the 60's with the design of the big v-8's heavier weight seemed to work, but now engines designed for the Ow/5w . (Of course engines where built so loose that compare todays motors they would be considered 75% worn.)
Back in early 70's a retired R&D engineer from Valvoline was telling me that 1950/60's tests using very light dino oils on heavy equipment engines and different bearing tolerances the crank bearings had much less wear.
Anyhow with Mobil 1's ablility not to break down under stress (film strength) and 0w-40 extra cleaning properties , I believe for me I'll stick with it.
The engine just feels freeier all the time and with the Pure One/FL 820s filter even after 5-6 months the oil staying cleaner.
I haven't been putting on that many miles in the last several years, but lots of short trips motor not getting fully warmed and it's still staying clean???? Then ever 3-4 months jump into the car and do 1000 mile trip which includes the race track type driving around Chicago to visit the grandson in northwest Illinois.
Paul
