-> EPA is the keyword!  If you read the charts (not the text) in the owner's
-> manual you'll find something like 'SAE 5W10 is recommended for the Arctic',
-> 5W20 for Canada and northern USA, 10W30 for mid-USA, 10W40 for southern USA,
-> and 20W50 for Mexico and the Carribean states'.

No such recommendation in my S10 owners manual. don't know what the Rwal
Shop Manual says but what you listed makes sense.


-> This info directly contradicts the "EPA stickers" found all
over under the
-> hood.  

-> Factory tests for EPA requirements are conducted with 5W20 at the factory
-> (under very controlled conditions), and they barely squeak by.  Using an oil
-> heaver than SAE 10W30, puts a _slight_ drag on the engine when cold, and the
-> computers cause the engine to run rich, thus flunking the EPA requirements.  To
-> hell with what's best for the engine in it's own real world climate!

 I suspected something like that but was leaning more toward the CAFE
miledge Standards. The vehicle running 20-50 will get less miledge than
the one running 10-30
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