Automobiles are machines, and working with machines sometimes means getting technical, at least technically. What is your most embarrassing technical moment, with cars or other machines?
Mine involved a simple oil change at a friend's house. That car used the common metal-can oil filter, but I forgot my oil filter wrench, and my friend didn't have one. So I use a large channel-lock style wrench and twist on the new filter. Start up the car, drive it outside, immediately find a sea of new motor oil that had just been inside my engine. I later found a new oil filter with holes from the wrench mounted on my car. It felt bad.
Photo Credit: The United States' Library of Congress, via Wikimedia Commons.