Even the most reluctant of car valeters needs screenwash. It’s a driving essential and vital for safety, as demonstrated by the number of cars which now have dash lights that indicate when the reservoir is empty.

So whether clearing road spray in winter or dead bugs in summer, you need screenwash, but it is hard to choose the right product, as packs and concentrations vary wildly. We tested 17 on a screen smeared with oil and insects, checked their resistance to freezing and worked out the cost for winter and summer mixes.