Over years of working in a mechanic shop and shopping Craigslist, I’ve noticed here and there that people will claim that their old car is still equipped with its original factory-installed fuel pump or fan belt or water pump or whatever, despite the vehicle’s high mileage. “Pulled the brakes apart today. The car is still using the original brake rotors.”
Usually this is 3 or 4 owners in.
Unless they have access to every service record from day one, and know that they aren’t missing any, how do they know that it’s an original part? Do they just see dealer-installed OEM parts and assume they’re the original ones? Kinda confused here. Maybe I’m missing something obvious.
I’ve never said that unless verified by either my knowledge (with backup documentation if there’s money or a trophy at stake) or manufacturer date code. Bosch has a three-digit code (although it’s alphanumeric, and could be only two characters before 1964), SWF has an alphabetical code, Hella has an alphanumeric code, Blaupunkt used alphabet until 1970, then made the switch to numerical.
My E30 had its original cap and rotor, both dated 1988. My E30 also had its original block because the block had the VIN on it. Most of the suspension bushings were original, as evidenced by condition. The fan clutch and fan are both original based on date codes.
My E36 still has its original radiator; the date on the radiator is older than the car.
Within my niche, vintage German cars, I can usually tell with a high degree of accuracy as to whether or not parts are original because I’ve seen a lot of original parts. Some of it even boils down to sealant application and selection; I can always tell when an early 911 engine case has never been split.
A lot of cost cutting/homogenization, as well as materials progress, has happened in the parts world, and original parts may have used, for example, a unique sheathing with a tracer (that may have originally been to increase burst strength), but modern hoses don’t need that reinforcement and the lines are now just rubber hose. Could that hose have been reproduced? Sure, but no one does that surreptitiously- there’s value to high-level restoration and reproduction.
And of course, there’s always the matter of witness marks on hardware. Look on the flats of the bolt heads and nuts- are there discolorations? Patterns in grease? Are the corners rounded?
I know this is much more in-depth than trying to figure out if a 2014 Traverse was driven gently, but it was nice to put out there.