The following is copied from the Owner's Manual for a 2004 Honda Rebel. The chart at the end would not copy, however, it shows 10W30 and 10W40 for temperatures ranging from -10 degrees Celsius (14 degrees F) to above 45 degrees Celsius (113 degrees F). So I use synthetic 10W40 motorcycle oil. A lot of folks that ride XJ's have used Rotella 15W40 for years.
JASO T 903
Servicing Your Honda
SG or higher
labeled as energy
conserving on the
Pro Honda GN4 4-stroke oil (USA
& Canada), or Honda 4-stroke oil
(Canada only), or an equivalent
Suggested oils are equal in performance
to SJ oils that are not labeled as energy
conserving on the circular API service
Your motorcycle does not need oil
additives. Use the recommended oil.
Do not use oils with graphite or
molybdenum additives. They may
adversely affect clutch operation.
Do not use API SH or higher oils
displaying a circular API ''energy
conserving'' service label on the
container. They may affect lubrication
and clutch performance.
Do not use non-detergent, vegetable, or
castor based racing oils.
Other viscosities shown in the following
chart may be used when the average
temperature in your riding area is within
the indicated range.
CHART DID NOT PRINT--SEE OPENING COMMENTS
2004 CMX 250 C Rebel--for the fun of it
2001 Honda 750 ACE--for the long rides
2004 Honda Aero 750 (Wife)--what can I say
1985 Yamaha XJ 700--for the old times