10w40 too thin imho

[shine]

i know the tolerences in our motors are tighter than the pushrod engines that normaly call for a 20w50. also, that our scoots are water cooled. i have a 07' 1600 nomad. i also know that it is normal for oils to shear, especialy since ours does double duty, lubing the transmission as well. right now, i am in fact, running the mobil 1 racing 4t 10w40. even though the synthetics are more stable against shearing than the petroleum based oils, they do shear as well. my owners manual states that 10w40 is prefered at all temps. my point is...even if the oil only shears a bit, which i think would be likely, heavy bike, often 2 up, fully loaded bags, un aero dynamic w/ the windshield, etc..it would then be a ? 10w35? 10w30? or worse? i think a good stout 15w40 or a 20w50 would leave a margin of error or safety. it could shear a bit or even a grade and still be within the thickness needed to protect our trannys and mills.. not to start a "brand" or syn vs dino war, i just know that other big twins have a thick oil for the motor, a stout, separate, usualy 80w90 gear oil for the transmission, and a thinner, 10w40 for the chain case. i am a poor man, lol, and i just want to make sure that i am doing the best i can for my nomad. i would be willing to trade a mile or two per gallon using a thicker oil that could shear a bit and still be protecting my motor. opinions? sorry i havn't been as much involved instead of lurking, but my home is a wreck and have to move completely out by this thurs..so i'm cramming it in now! i hope i havn't put anybody to sleep! ::) :-/