That little rattle, or the light on the dash, can seem harmless right up until it isn't. Not long ago a customer came in with a minor issue that had quietly snowballed into a £480 bill, because getting it looked at felt like money spent on a car that seemed fine.
We hate seeing that happen, and it is exactly why the plan exists. If the check is free, you ring the day the rattle starts. If the scan is free, you do not drive around with a light on for a month hoping it clears. Most of the four-figure jobs we see started as something small that somebody drove through.
It is not for everyone. A nearly new car under warranty that barely needs anything is cheaper pay as you go, and the calculator further down will tell you that to your face. The plan is for people who use a mechanic more than once a year and would rather never wonder what a visit will cost.
Catch the problem while it is still small, instead of fixing it after it has broken. That is the whole idea.