They should have come up with something better for Darnell's death
Darnell's death was even less believable than Buddy Repperton running straight down the middle of the road rather than veering off to the left or right into the field, and even less believable than Christine having enough traction to force "herself" into that too-narrow opening to kill Moochie.
No one voluntarily gets in and sits down in a car that was recently engulfed in flames, still so hot that smoke is pouring off it and the door handle instantly burns your hand, complete with a sizzling sound. He would have felt a blast of hot air when opening that door worse than you get when opening the door of a hot oven (just think of how hot a car interior is when it's been sitting in the sun on a hot day with the windows rolled up; now imagine if it had recently been engulfed in flames and still had smoke rolling off it), and the smell/fumes from all the burning seat foam rubber, vinyl seat skins, rayon and nylon carpeting, paint, etc., would have been horrendous.
Even if he, inexplicably, wanted to brave the probably 250-or-more-degrees air temperature in there and the potent smell/fumes just so he could pretend he was driving like 5-year-old kids like to do, the steel seat springs would have burned his ass just like the door handle burned his hand.
Even as a kid I found that scene completely unbelievable. And even if the car had had time to cool down, the scene still wouldn't have been believable. Why would a grizzled, cantankerous old junkyard owner be interested in pretending to drive a trashed car, especially one that's been on fire and will leave soot all over your clothes?