Draper Anti-Freeze Tester 61794

Protected by a handy plastic case, this Draper is smaller than disc-type rivals. It has a floating glass tube, with a graduated scale covering between -5 and -40 deg C.

You read the result at the water level, which is tricky, and need to take care to remove bubbles. It was close to the 33 per cent readings, but a little low at 50 per cent – not great, although better than over-estimating the protection.