Every week when I explain to a customer what a diagnostic inspection has revealed about their vehicle and what needs to be replaced and/or repaired in order for the vehicle to run or operate properly, I always recommend factory quality parts in the estimate.
I don't do this because the business I work for makes more money on factory parts (or original equipment manufacturer -- "OEM," for short), because I get a potential bonus for selling these parts, or even because they save the customer money. In fact, using factory quality parts probably missing on all three counts, and selling a universal aftermarket parts probably would do all three. There are a couple of useful things customers should know about factory quality parts and auto repair.
By "factory quality" parts, I do not mean "dealer only" parts. The same parts can, in over 90% of the cases, be purchased from the vendor who makes them for the dealers and at very reasonable prices. I have attended factory schools for major European, Domestic, and Japanese Manufacturers since the 1980s, and in these classrooms design engineers explain the development process of a new automotive system. In almost all cases, some time is spent on the testing early prototype systems and analyzing failures. Many failures involve problems with component design, the materials from which they are manufactured, and in some cases, the manufacturing process itself. Usually, after 2-3 years of lab testing and field trials, an automotive system and its components have been developed and tested to the point where the failure rate has been reduced to very reasonable minimums. This rigorous process results in factory quality parts.
When an aftermarket parts maker creates a "Universal Oxygen Sensor," they have to generalize the design specifications, often to a significant degree. I recently worked on a vehicle that had been to 4 or 5 shops with a mysterious "Check Engine Light" and misfiring problem. I did some research and found that the Oxygen Sensors for this vehicle had specific heat ranges, like spark plugs. When I checked the newly installed Oxygen Sensors, they were generic, aftermarket sensors. I installed the absolute proper sensors and the vehicle ran flawlessly. The customer lost over $1500.00 just trying to solve this mystery. The generic sensors worked for about 3-4 months and then became imprecise and caused problems but did not set any Oxygen Sensor codes. How much was really saved by the shop that put in the substandard Oxygen Sensors?
Next: "Factory quality Oxygen Sensors, ok, but but we can cut a few corners on Brake Parts, can't we?"