I have been using synthetic for awhile now, I pay around $7 a quart, I have used both oils, and a retired auto mechanic now with a moped hobbie. I can say with experence the synthetic is worth the little extra, NO plug fowling,NO ash which is a carbon build up, bikes have a free`er(less drag) feel to the motor and run cooler. I don`t sell the stuff, but after using over a period and do a teardown for regular maintaince, it sold me! How long before a rebuild, is yet to be seen. Doug D.