Considering a few things before buying a used engine? First of all, try to search for the exact specifications for your vehicle, things such as VIN or make, model, and year. Check the local junkyards and stores for the same measurements and then ask the salesperson questions such as: "What about mileage?" "Does it pass compression tests?" "What about the warranty period?" You can also entertain the possibility of orders made directly online. But do protect yourself by checking reviews/ratings of the sellers as well as the returns policy. Try eBay, LKQ, CarPart.com, and so on. Whichever the case, check compatibility and warranty, whether locally or online. Being cautious encourages both saving and extending the driver's life.