The cars are fine, the counter service is fine, all is fine - except that, if you want to extend your rental, be aware that you can only do so for 5 days online or by phone (even though the website says you can extend up to 28 days). You have to go back to a branch to do that. In a mission to reduce their customer service levels, Sixt closed their branch in Oviedo city, thereby requiring me to make a 100km/75 minute detour round trip just to make a longer extension. Stupid in this day and age of doing everything online.