I expected Cop Car to be more of a horror/suspense film. Like one of those movies where the teens are pursued down empty highways by maniacal truckers. You got two kids stealing a crooked, murdering sheriff's car, and him trying to get it back (because there's a live drug dealer in the back he needed to kill a dispose of).
But really, it's more absurd than anything else. Kevin Bacon's the sheriff, and he spends the first third of the film running across empty pastures in Colorado, trying to find another car, so he can start tracking his cruiser down. And the guy was stupid enough to go off and leave his keys in the car. I never get out of my vehicle without making sure I've got my keys, and I don't have a ton of firepower in the back seat, or somebody tied up in the trunk.
Meanwhile, the kids are trying to figure out if they can smash through gates, daring each other to get the car up to 100, and screwing around with the guns they find in the back seat. When they eventually release the drug dealer tied up in the trunk, he uses them to lure the sheriff in, then does this absurd dance of running around, trying to find some place to ambush from. He tries using the bathrobe he's wearing like one of those suits snipers make, then tries hiding behind a power pole, before deciding "behind the windmill" is the optimal spot. I will leave how the climactic chase ends for you to find out on your own.
I spent a lot of time during the film trying to decide if the two kids are realistically stupid for their age. There are a lot of scenes of a character or characters moving through a vast, empty space, you have to do something to keep the mind occupied (which explains why the kids would steal the car, nothing better to do). I guess they are. I'm not sure I would have understood driving all that well at their age, though I did know about guns having a safety you have to turn off to fire. I'm guessing they didn't have a parental figure who liked to hunt.
Cop Car does what I think it set out to do pretty well, it just wasn't what I thought it'd be.