When it comes to providing maintenance on your beloved machine, don't cheap out on fluids. Motul motor oil is some of the most trusted motor oils utilized by professional race teams, to the neighborhood grassroots racer. This is their 15W50 technosynthese which is a fancy word for synthetic blend designed to provide optimum protection against friction and wear. 
This oil can be used on large displacement engines, turbo diesel engines, and engines with higher mileage.
Note that this is for 1 US quart.