A factory part breaks or wears out. Independant shops I have used insist on replacing with the same OEM part when reputable aftermarket parts are available at less cost. Given hard evidence of particular factory part unreliability is in hand, it seems logical to replace with a part from a second source and the "OEM only" practice appears dubious.
Why would an independent shop prefer OEM parts?
I ask because GM, for example, calculates their parts are only reliable to just 36k miles. It seems customer/shop enthusiasm for OEM parts exceeds the that of the analysts in the factories' own warranty department. Is there something motivating the independant shop business other than preceived quality (easier to order?, faster delivery, distributor floats payment or extends credit?, higher priced parts allows more markup?). Or are independant shops really have data and expertise to do a proper lifespan analysis, (with numbers) that show OEM parts last longer?