Myths About Buying Replacement Truck Parts If you’re considering buying second-hand truck parts, keep in mind that trying to save a few bucks on non-OEM (Original Manufacturer Equipment) parts could actually be harmful to your equipment and may even be illegal. Furthermore, some replacement truck parts claiming to be OEM parts are not OEM at all, and this can be a big headache for fleet supervisors trying to determine precisely which part fits perfectly as a replacement for their vehicles.