Matt

I think Fred's oil change intervals are too long for our XT600's.

My Clymer manual recommends 4000 mile ( about 6000 Km) intervals.
As the bikes mileage increases, to say beyond 20 000 miles I personally would reduce the interval to every 3000 miles, using mid priced semi-synthetic oil.
You could possibly extend the interval by using fully synthetic oil, but I'm not convinced that the shearing action of the gearbox on the oil doesn't reduce it's viscosity just the same.

Something else worth mentioning is how to check the oil level if you're not familiar with the quirks of dry sump engines.
You need to check the level on the dip stick which is part of the oil tank filler cap when the bike has been running for at least 5 minutes, and been idling of a minute, and you need to check it within a minute of switching the engine off, so remove the side panel before turning it off.

Yamaha say you can check it much sooner, and some people say that if the level drops after the engine is switched off the oil pump is worn badly, but the level on my bike continued to drop after the engine had been turned off after I had fitted a new oil pump.
If you don't do this it appears that the level is too low, mine sometimes won't even reach the bottom of the dip stick even if I screw the filler cap back down. Initially I was topping it up only to have oil come out of the oil tank breather a few miles later!

Also be sure to carefully measure the quantity of oil you refill with after an oil change, to the nearest 0.1 litre, as the dip stick won't till you when you have the correct quantity for a few miles !

Good luck and have fun

Mark