Shouldn't we all be using a 10W40 rated SF or SG? I don't like to go against manufacturer recommendations when it comes to motor oil. The last time I changed my oil I got the exact Suzuki motorcycle oil recommended for my bike. I don't see why anyone would want to test other oils.
After a brief google, I found this:
http://www.ibmwr.org/otech/oilreport.html. I think it's worth a read. Apparently, the SG rated oils had additional phosphorous and zinc, which the EPA didn't like because it made catalytic converters less efficient. Therefore, they came up with a new standard, "SM", which is lower in these two elements. When it comes to my bike, I care about what is effective in promoting engine longevity, not the EPA.
Here's another article that google turned up:
http://www.bikenomads.com/wiki/index...r_oil_in_bikes
Here's a small sample from the above link:
"Recap - Synthetic Oils
Recap - synth oils meant for cars when used in bike will cause clutch to slip because car synth oils have friction reducers which are not requried in wet clutch motorbikes. The oil in wet clutch motorbikes need the oil only as a coolant not a lubricant . The lubing is required for the engine and not the clutch in this case. Hence use only specially formulated motorbike syth oils and not mobil 1 etc in bikes. Synth oils are available for mobikes specifically - ex motul 300V. "
And, one more quote:
"Q: WHICH FOUR-STROKE RACING OIL SHOULD I USE?
A: If the bottle of oil doesn't list that it is an API SG Service Category or JASO MA spec, it's not good enough for your motocross bike. Although a bottle of oil might say "motorcycle specific" or "safe in wet clutches," the best endorsement is the API SG or JASO MA designation. It's better to be safe than sorry. "
Frankly, I don't see why you'd use anything other than what the manufacturer recommends: Suzuki 10W40 SF or SG rated oil.