New to the Forum and looking forward to do some traveling in the near future.
Great Forum with a lot of good information.
I would like some recommendations on reliable car rental companies in Oviedo, Spain.

Sixt

We were not in Oviedo, rather rented in Granada, then later when leaving Sevilla & drove North to Salamanca. We used Eurocar. But started out as Enterprise which it seems was same company. Be ready for slightly different model than your 1st choice ( just in case). And if you are not already accostumed to cars that automatically stop engine when idling, ask about disabling that feature because it's a pain in hilly areas when you are not used to it.

We are in the process of looking at rental cars in Oviedo, too. There doesn't seem to be a lot of great choices in the city-- more if you look at Gijon and the Asturias airport, but we'd prefer picking up the car in Oviedo. We have had decent luck with Enterprise in Europe, but on our last Spain trip we rented from Enterprise in Madrid and the clutch burned out around an hour into our trip. Enterprise eventually came through with a new car, but dealing with the issue was not straightforward. But it seems like the best of the options for picking up in Oviedo, so we will probably end up trying our luck with Enterprise again.

I always work with gemut.com, which works with AutoEurope, a broker for several reputable companies (e.g., Europcar, Hertz). They're based in Oregon and their customer service is outstanding!
https://www.gemut.com/

Thank you for your recommendations, I will be looking at all of those options.
I will also prefer to pickup in the city because I will be taking the Ave from Madrid to Oviedo.

Than you all for you recommendations, I will be looking at all those options.
I also prefer to pickup the car in the city, because I am taking the Ave from Madrid to Oviedo.