opinion-please read all

I'd vote for the PM to the seller first THEN post on the site.

However, if your argument involves questioning generally accepted information (like the white books) it is unfair to put that on the seller. When I list a part I'll say "the parts book lists this as correct for..." If you sent me a PM saying the parts book was incorrect, I'd ignore you as well. And I wouldn't want a huge discussion on my "for sale" post over whether the white book information is correct. and I CERTAINLY wouldn't want to be called a "ripoff" because we disagreed on whether the info was factual.

It's like arguing the information listed in price value guides. I disagree with much of it, but the info is considered the industry standard. Until Govier issues a revision or correction (or until someone else publishes a competing guide which becomes accepted as more accurate) it's what we go with.

BTW this would be a good time to reiterate the idea that sellers should be able to remove their posts if an item is described wrong or the post gets out of hand or after it is sold.