Hi am based in Carson city Nv. Averg. In the 80 degrees at 4500 ft. Run up to lake tahoe at 9/10,000 ft.
yep full synth is best could use the 10/50 but 10/40 should be fine. Got a 2007 Speedmaster myself they are lots of fun, enjoy it.
If std recommended grade oil is 5w30 i wouldn't go more than a 10w40...10w50 is likely to load up the oil pump and make the PRV bypass too much....semi or full its up to you.
Fully synthetic is ‘best’ if you do the mileage between changes to justify it and run in high temperatures. The fundamental difference is that fully synthetic oil loses its physical structure and thus its lubricant properties less quickly. Air cooled bikes are harder on their oil (the primary coolant in the hottest parts of the engine) than more thermally stable water cooled bikes. You need to decide if the price premium is worth pretty marginal performance benefits......and the oil vendors know we baby our bikes! Your real guarantor is the SAE and JASO number......
