2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 79Get this manual
MAINTENANCE Other viscosities shown in the chart may be used when the average temperature in your riding area is within the indicated range
Make sure that the O-ring on the engine oil filler cap is in good condition and replace it with new one if necessaryReinstall the engine oil filler cap
ENGINE OIL FILLER CAP
OIL AND FILTER CHANGE