For years I used "motorcycle oils" that cost between $7-10 per quart, until I discovered Rotella. I will continue using Rotella T4/T6 15w40 in my shared sump dirt bikes until I have good reason to change. They are in the spec'd viscosity range, they meet the performance specs of MA/MA2, and at $12/$19 per gallon it is impossible to beat the quality and price. My only "problem" is... I like the smooth shifts with T4 but I like the full synthetic durability of T6, and T5 semi-syn is not labeled as MA/MA2. So I mix T4 and T6 50/50 with awesome results.