This arrangement kind of makes sense - IPA is used less in #screenwash as it costs more, and is also more likely to strip protection such as wax from your cars paintwork.

Also tested Tesco screenwash which read same as #Holts (-7 to -10 Celsius) - not surprising, its made by them (this info is buried in the Holts MSDS website) and Prestone concentrate (also Holts) at -18 Celsius (so label is true).

Which means the cheap stuff should be OK for fleet cars in winter if appropriately diluted..

I double checked the #screenwash scales of the #refractometer with spiritus (denatured ethanol), diluted from approx 92% (according to Tesco) to 60%, which should have a freezing point of -37,5 degrees Celsius

I did also try diluted IPA but readings were way off, it seems like *both* the scales on this one are for ethanol mixtures and you are supposed to take an average reading (this isn't mentioned anywhere in the instructions for this or similar models, even the pricier ones!)