What is the name of this movie?

It’s a movie that came out in the late 80’s or early 90’s. I can’t remember who was in it, other than there being some big names, like I want to say Dustin Hoffman, but I could be totally wrong.

The plot of the movie.. A guy is working at an advertising agency and discovers by accident that telling the blatant truth in ads is a bigger hit than simply trying to market things. The ‘honest’ ad slogans are hilarious. One of them had to do with Volvos being boxes on wheels or something like that.

I want to see this movie again, as it was really funny and clever. Does anyone know what it is??