Well I just tested my anti-freeze with the Lidl 99p antifreeze tester, and it goes to -40 C. By my calculations, it should be -39 C 50% mix
So well within the limits of error:thumb2
The Lidl instructions are not that clear, there is a small piece of white tubing at the bottom of the unit, you don't need this, it is used to push in the end of the tester as shown on the diagram, if required.
I think they use the same instructions for when they sell a battery tester.... (place in appropriate resevoir...)
When you sample the antifreeze, there will be bubbles on the hydrometer ( the stick), tap the unit until these float off, much easier to use than my last one.
To gain confidence with it, test tap water, it should remain at the bottom.
Wash it out thoroughly after use.
If you empty the radiator and header tank, flush if possible, but you will just be able to get 5 litres in of the concentrated antifreeze, giving 50% strength and protection down to -39 C :thumbs
I just placed my plywood over the top part of the grill this morning, it'll be there now til end of Feb.
It is behind the plastic grill, very neat, painted matt black.
I hope all is well with the engine and you were lucky enough to get it sorted.
Best regards, Rustic