Goldcar comes off as being ridiculously cheap compared to other rental car companies as TFN, but there's reasons why:
1. You must find the spot to meet up with a Goldcar representative and it is not marked anywhere in the airport, or even at the destination. Btw, its is on floor -2 of the customer parking lot at the "meetup" area. We found other lost-looking travelers and found that we were all looking for the same thing. Luckily one had a cell phone and called them for a pick up.
2. They charge you 70 euros for fuel upfront without a refund for unused fuel
3. They give you a ridiculously fuel-efficient car which will not use up the entire tank, even if you drive up and down Mount Teide 10 times. We had the car for 3 days and drove to Buenaviste Del Norte, Los Cristanos and back and barely used 1/4 of a tank of fuel. I'm in favor of fuel efficiency, but not at my wallet's expense.
In the end, I would have preferred renting from another rental company that is more transparent and easier find after a long flight. I probably didn't save any money with using Goldcar instead of Avis or something else, due to the fuel charge, so in the end, it wasn't worth the "savings"