OEM, aftermarket, reman, used

Parts get sold in grades, and the labels are used loosely enough that they mislead people into overpaying on some items and underbuying on others. Here is what each one actually means.

OEM

A part sold in the automaker's box, through the automaker's parts network, at the automaker's price. It is the same component the factory installed. You are paying for guaranteed fitment and a name on the box.

OE supplier, the one most people miss

Automakers do not manufacture most of their own components. They buy them from suppliers, and those suppliers frequently sell the identical part in their own box for meaningfully less. Same factory, same line, different label. When you can identify the original supplier for your part, this is often the best value on the board and it is the grade least understood by casual buyers.

Aftermarket

Made by a company with no factory relationship to your automaker. Quality across this grade ranges from better than original to genuinely bad, and price is a weak signal of which. Established aftermarket brands with long warranties and published specifications are a different thing from an unbranded listing with no manufacturer named at all.

Remanufactured

A used component disassembled, inspected, worn parts replaced, and tested to a specification. Common for alternators, starters, calipers, steering racks, and transmissions. Good reman is a legitimate value and often carries a real warranty. Expect a core charge, which is a deposit you get back when you return your old unit.

Used and salvage

Pulled from another vehicle. Reasonable for body panels, interior trim, glass, and hard parts that do not wear in a hidden way. A poor idea for anything with a service life you cannot inspect, because you are inheriting an unknown number of miles.

Where each grade earns its money

• Pay up for safety critical parts, anything holding a wheel or stopping the car, and for components buried behind eight hours of labor. Doing the job twice costs more than the part ever will.
• Go middle on wear items you replace on a schedule anyway. A quality aftermarket filter, pad, or plug from a named manufacturer is a sound buy.
• Go cheap on cosmetic and non structural items where a failure means an annoyance instead of a tow truck.

The number that matters more than the grade

Warranty. Read the actual terms, not the headline. A lifetime warranty that excludes labor, requires you to ship the failed part at your expense, and dies if you sell the car is a different product from a three year warranty that covers the job. The terms are published. Almost nobody reads them.