In "Precious and Grace" by Alexander McCall Smith, the author draws a parallel between engines and human beings, emphasizing the need for regular maintenance and care in both cases. Just as an engine requires oil changes to function smoothly, people also need self-care and attention to their well-being. This metaphor highlights the importance of nurturing oneself and others in life.

The narrative continues by exploring how both engines and individuals perform best when treated with kindness and respect. The idea that moving forward is preferable to going backward reinforces the notion that progress and positive growth are essential for both machines and humans. This insightful comparison serves as a reminder to embrace change and foster development, offering a comforting perspective on life's challenges.