Hi Doug:
Good points on the application and the results from the rest of the world.
I try not to be the cynic but to approach this issue with an open mind. I'm sure Mobil 1 0W-40 is a fine oil and perhaps could be used year-round even in my climate.
I would even be willing to try Mobil 1 0W-40 just to see how it holds up. It's just so hard to get around here, however I am planning a trip to Minneapolis soon, maybe I could find it there.
The big challenge I have is the extreme cold winters I have to deal with. Thanks to the numerous startup, warmup, and short driving cycles, even bypass filters are limited in what they can remove.
So I'm usually stuck with OCI of every 6 months or so.
A BITOG forum member posted the link to the official EPA memo on "fuel saving" oils and I nearly flipped:
http://www.epa.gov/otaq/cert/dearmfr/ccd0112.pdf
Now if I understand the math correctly, you take the result of the 16 hour test, the result of the 96 hour test, and ADD THEM TOGETHER.
Then you add on 0.5%
So even an oil that does ABSOLUTELY NOTHING for fuel economy is still ranked as "improving" fuel economy 0.5%. Some folks go on and on about how this magic oil improved their fuel economy 1-2 MPG, say 20%. Pure rubbish.
I still find it suspicious that Ford and Honda in Europe do NOT approve or recommend an xW-20 oil.
For more on oil viscosity and the effect on the motor, check out Machinery Lubrication Magazine:
http://www.machinerylubrication.com/article_detail.asp?articleid=518&relatedbookgroup=Maintenance
http://www.machinerylubrication.com/article_detail.asp?articleid=529&relatedbookgroup=Lubrication
So there is nothing wrong with running a heavier oil as long as the lower MRV values are not exceeded. Since I believe in matching viscosity to climate, I run a very thin oil in winter and a heavier oil in summer while towing.
So try a HDEO like a 15w40 or a synlube HDEO like Rotella T 5W-40 or Delvac 1 5W-40. Or Mobil 1 15W-50, I've used it in my Vortec 5.3 towing 7,000 miles and it worked great.
Jerry