Wow. That's terrible. I'd go over every square inch of that motor to make absolutely certain that it's not leaking somewhere.

However, a leak that large should be immediately obvious. Then again, so should that level of oil burning. The oil does not just disappear though, it's either being burned or leaking out.

Keep us posted. My hope & guess is that there's a leak, but that may be Pollyanna-ish.