Different types of motor oil ?

[bigdog]

Can someone please explain to me what the difference is between regular motor oil and 'high-mileage' motor oil ? I suspect it is hype and or just marketing?

Also, the differences and advantages between synthetic-blend and full synthetic ?
My car just turned 92k miles, and wondering if I should use the 'high-mileage' variety ?

I've always used a standard high quality oil like 'Quaker State', Pennszoil, Valvoline, in the standard 5Wx30 viscosity. I've checked some websites and for my 2011 Subaru Outback, they are suggesting a 'full synthetic' oil.

The Valvoline website in particular states
"Higher-mileage oils are formulated with conditioners that flow into the pores of the engine seals to restore their shape and increase their flexibility. Most rubber seals are designed to swell just enough to stop leaks, and oil refiners pick their "reswelling" ingredients carefully.".

I do know, once you change from a standard motor oil to a synthetic (or blend), you can
never go back, and the viscosity must be the same, and recommended change intervals are the same.

I plan on keeping my car forever, or until it wears out, so would appreciate folks feedback, especially from you motor-heads and engineers.

Thanks !