Something I heard on the TV recently, someone well known, (?an MP?) had phoned a relative to ask what it means when the gravy boat goes red.
Years ago I had an ageing professional neighbour, she always drove a new-ish sporty Japanese car and changed it every 3 years. I returned from work one day to see another neighbour with his head under the bonnet of her car and minutes later walking away roaring with laughter. She'd asked him to look at her car because it had overheated on the way home from work, in addition to that she couldn't get it to go any faster than 60mph. During the course of his diagnosis she'd repeatedly pointed to the revs counter when talking about the speed. He eventually arrived at the conclusion that she'd driven back home along the M4 in 3rd gear red-lining it at 6,000rpm thinking she was doing 60mph!