Replacing a blown or worn-out engine is one of the most expensive repairs a car owner can face. For Nissan drivers, one of the smartest ways to restore a vehicle without draining your bank account is to invest in a quality used Nissan engine. But before you hand over your money, there are critical things you need to understand — from compatibility checks to mileage, warranty coverage, and where you actually source the part. This comprehensive guide walks you through everything.