I don't know about you guys, but my Prius burns as much oil as it does gasoline (it's a joke; or is it?). That has to be why it gets such good mileage. I put a quart of oil in every fourth fill up. Any else burn that much? I know it's burning it too, cause I got a misfire code a few months ago and when I replaced the plugs and coils the plugs were caked in oil.