Your letter on March 23 regarding car hire fuel charges is important and affects many visiting Algarve.
I rented a car using Car Trawler and was ripped off in this way. Each firm blamed the other, but basically my relatively reasonable car hire charge suddenly turned into a very uneconomical option and I returned the car almost half full yet ended up effectively paying twice for the fuel and at a massive €1.80 a litre.
This should be controlled and will certainly leave a very bad taste when others get trapped in this way. I will not be caught out next time.