Robert DeNiro’s curmudgeon roles are different than his others, there’s a sour aspect to them that reeks through the production (case in point, he rendered “Joy” into joylessness). Dirty Grandpa would have you hope to see a randy, gregarious DeNiro who goes for broke at a Daytona Beach Spring Break but it’s really just another curmudgeon part, a lá, bad mood DeNiro. Of course, anything past the “There’s Something About Mary” era some eighteen years ago (the raunch movie that got the sour and sweet formula exactly right) means it’s going to be a gross-out comedy above anything else, and this movie – perhaps the worst I’ll see all year – is as gross, smarmy and disgusting as they get. Not to mention, being tone deaf, vitriolic, xenophobic and hypocritical about its’ proposed sweetness.

Uptight grandson Zac Efron is a mover and shaker at a law firm. The whippersnapper is about to be married to an even more uptight bride (Julianne Hough). Somebody needs to teach this kid how to abandon himself and live life to the fullest – who is gonna coach him in that? DeNiro has just laid his deceased wife to rest, and post-funeral, he’s playing with himself to a dirty porno. Oh, beyond that scene, he’s insisting that his grandson drive him to Daytona Beach for some serious business (Never mind what that is – I can’t remember an hour later), yet it’s really just to sew oats, and inspire his grandson to chase some tail, too.

I knew “Dirty Grandpa” was an awful vulgar comedy from the get-go. I was never more disgruntled than during a child molestation joke where a kid is yanking at Efron’s privates region, miming a head-jerking motion that, by pantomime, is mistaken for fellatio at a different adult’s vantage point. Aubrey Plaza is one of the gals the boys meet on the road, and while she’s vulgar too, I oddly, respected Plaza because I think she’s the one actress in this world who is dirty-minded off-screen as she is on, and there’s something about her, something at least genuine about her acting that lends some cred. A critic I admire, Glenn Kenny, who had his own amusing wrath for “Dirty Grandpa,” noted that Plaza’s lines are on a smarter level than the rest of the cast and it is presumed that she ad-libbed most of her dialogue. That sounds right.

So I hated the rest of “Dirty Grandpa” that hadn’t anything to do with Plaza’s scenes. I should mention a climactic nutty car chase that’s inspired by the sex comedy car chases in begotten duds from the 1960’s, but this one here – so ineptly shot, so lamely arch – that makes something like “Sex and the Single Girl” (1964) with Tony Curtis seem like a class act in comparison. Of anything, I fret over DeNiro’s willingness to debase himself with this comedy when he could be holding out for more respectable work. However, I hold the right to say that I still think “Grudge Match,” DeNiro’s curmudgeon variation at rock bottom, is still the worst movie he’s ever done. By a small margin.

103 Minutes. Rated R.

CRUDE COMEDY / DUMB TEENS / LATE NIGHT YUKS

Film Cousins: “The To Do List” (2013); “Last Vegas” (2013); “Grudge Match” (2013); “Bad Grandpa” (2015).