In 1957, the Socony-Vacuum Oil Company – now known as Mobil – commissioned a documentary to cover that year's Pikes Peak Hill Climb. It was called No Margin For Error, and if you needed more proof that old school racers were both hugely talented and monumentally insane, here you go.
The mini-doc follows Jerry Unser, who won his class that year, and covers everything from racing to pitstops to the importance of choosing the right oil (natch). The Pikes Peak Library has a few other interesting vintage videos on file, but this is the pick of the litter. Props to Silodrome for finding it.
Bonus video of a 1955 helicopter ride up the snow-covered mountain: