I've always headed southeast on SR89 from Mount Shasta to SR44 to Susanville. When I head up to visit my sister near Medford and the shortest time is not of the utmost importance, this route avoids the mind numbing I5. Mentally it seems to take less time.
KTM 950 SE, KTM640 ADV ( Hibachi, risen from the ashes)
KTM520EXC (broken), KTM 400XC (the replacement)
Honda ST1300 ABS (newest addition to the stable)
STOC #326 IBA #217