We recommend original equipment manufacturer (OEM) parts because they were designed specifically for your vehicle. Most automakers also back up their OEM parts with a one-year warranty. And if you get your car repaired at the dealership, they'll usually stand by their labor as well.Aftermarket parts on the other hand can be cheaper, but they're also less likely to deliver peak performance. An aftermarket part is any part or accessory for a vehicle that isn’t sourced from the car's maker.