So, yesterday night Sarah was complaining that her back was a bit itchy, so asked me to scratch it for her. This is a Thing that happens from time to time. No problem. After which she asked me to rub some E45 in. This also is a Thing that happens from time to time.
However - and whether this is due to Sarah being doped up on a combination of painkillers and muscle relaxants, or just a Freudian slip (given that she's a bit of a gearhead, I suspect the later - she was, after all, reasonably compos mentis at the time) - what she actually asked me to do was to rub some WD-40 in.