Next, you should ask exactly what the warranty covers. Fly by night companies will promise you the moon. Legitimate companies who actually pay out in the event of a warranty claim will restrict what they cover to the actual engine. Phrases like "the internal lubricated parts," "no gaskets or seals," etc should come into play. You shouldn't expect things that are attached to the engine to be covered, and you shouldn't expect maintenance parts to be covered. Only the actual engine itself will be covered under a warranty.