Fluid Toll in Spain

[DAC and Jan]

Currently touring Spain and was informed that the Spanish now have a “Fluid Toll” on some motorways? It seems that it informs you on the overhead gantry and you have to pay at the next service station or beyond but the day in question.
It is only €1 or a bit more but still a fine if you do not pay!
Has anyone come across this or has it been discussed and I missed it
Advice gratefully received
Great services called ‘Tienda’ (24 hours)
at Avenida del Pinatar San Javier Murcia
Water €2 Big Launderette and car wash so
Lola ( not the wife) but our motorhome had a good wash and brush up while waiting for our washing

 

[Badknee]

Not heard of that but I have seen new toll booths being built.