Ten thousand miles on synthetic engine oil, fresh filter and highway riding poses no engine danger for air or water cooled singles or twins. Try some in your air cooled lawn mower engine and you'll see what I mean. Name brand synthetic engine oils have higher Noack scores and typically don't shear nearly as quickly as non-synthetics. If you want even longer OCIs, use automotive synthetic engine oils that contain more robust EP additive packages. You want really tough engine oil? Try HDEO rated for diesel engine service. Shell Rotella, Mobil Delvac or Delo 400 in 15w-40 viscosity...$12.00 per gallon most anywhere. The OTR truckers typically run these oils for 20K miles and up to 50K miles in high HP diesel engines.