Indeed, the oil a Yamaha dealer would use when servicing your XT is Motul 5100 10w40 semi-synthetic (AKA Yamalube).

Any decent JASO/motorcycle-specific semi-synthetic will be perfectly adequate for your bike.

You can also use fully synthetic motorcycle oil, but realistically you're better off using a semi-synthetic and using the saving to fund changing the oil more frequently, say every 5000Km.

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