I say he's Full of Hogwash.
Just did an oilchange on the vibe in my sig.
last August 25th, i put 4.5 qts of Pennzoil Platinum into it with near as i can remember, 175k mi on the dash.
April 11, i drained that out (did spill a little) and haven't Drained the filter, but I got just over 4 qts out of it. (179,028mi on dash)
and this is an engine that typically loves to consume oil as they "get up there" (Toyota 1zzfe 1.8l)
the real question though boils down to why you want to switch to Synthetic anyhow. what are Your Reasons? what are your driving habits like? etc.
will syn really benefit you in some way?