Oil weight temp range

I was looking through the yamaha service manual for my 04 yz450f and found that yamaha specifies an oil weight range for USA and Canada,(20w-40 for temps above 40 and 10w-30 for temos below) and then a second oil weight range for the rest of the world,(tons of weights across a broad temp range with 10w-40 being the most versitile) whats up with that? Is this another EPA mandated deal?

It is an EPA deal. Has to do with wear reducers formerly found in SG oils, which are no longer in the current SJ/SL spec. Use a 10w-40 oil with a JASO grade MA. It's the equivalent of an SG with improvements. See my elaborate response on this subject in the recent thread "what kind of oil do you use?"

A side note; the Golden Spectro petrolium/synthetic blend is still classified SF/SG and is also listed as JASCO MA. I'm sure there are other oils that still fit this catagory.

True. Golden Spectra 10w-40 is what I use. Motorex makes JASO MA graded oils too, I hear.

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