The act of an individual acquiring hot gravy and pouring it down into their own urethra and then inserting a Kit Kat Chunky to fill the tube up.

Shortly after, when the time is right, the individual will take out the Kit Kat Chunky and the gravy will cascade everywhere.
"Ross, have you ever done The Swindon Oil Change before?"
by Dyluxray June 8, 2020
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The act of pouring hot gravy down your urethra followed by a kit kat chunky, then pulling the chunky out and watching the gravy spurt out after it.
Did you hear Smith did the Swindon Oil Change last night?!
by SWOM June 8, 2020
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