I have used duralube a few times in my cars. Two times, on a 4 runner and F250 diesel, we thought the tranny was needed replacing, it would slip really really bad and not shift, etc. we changed the fluid and filter, added a quart of duralube tranny fluid conditioner and it worked <shrug>. so i have to beleive in it.
i never ran my car out of oil <knock on wood> so i dont know from first hand expereince on that issue.