OEM is the manufacturer, not the part itself. The part is the OE (that's why the "OEM part" example above has to be seen together with the rest of the text - the part is from an OEM, but it's not in a blue box, for instance).
It's "Original Equipment Manufacturer", not Original Manufacturer Equipment. For our Volvos (and never mind that I used BMW as an example up there - the terms are the same):
OEM = Original equipment manufacurer
OEM part = Parts from the original manufacturer who has a contract with Volvo.
OE = the parts the Volvo left the Volvo factory with (i.e. parts from the OEM, installed by Volvo)
AFTERMARKET = Parts that will fit the Volvo, but were NOT manufactured by an OEM.
Just to clear one thing up - if you buy an O2 sensor from a Volvo dealer, in the blue box, and you buy one from a Bosch Service shop... which one would be more expensive? My bet is that the blue box is gonna cost you. So an OEM part (the Bosch sensor, bought at the Bosch Service shop) will be cheaper than the OE sensor (the Bosch sensor, bought in a blue box at the Volvo dealer).
So we basically all agree, sort of.
You're right to say that trusting the letters "OE" on a box is a mistake. Like I said, those Murray thermostats may be OE for another car brand, and to that brand, Murray might then be the OEM, but not for our Volvos. It's a damn jungle, man.
- S
