Yesterday when renting a car at Sixt Heathrow, we originally booked a Skoda Superb Estate. When renting the car, the waiter said the car was too small and tried to upgrade us to a BMW. I refused. The car looked very good and the boot was big enough to fit all four of our suitcases. However, the car showed that the tyre pressure was not enough, so they gave us a Mercedes 220 instead. But the car screen showed that we had to add AdBlue when we drove more than 700 miles. The waiter said we didn't have to worry about it. After we started driving, the screen showed that we had to add oil the next time we refuelled. After driving for an hour, we arrived in Oxford and the car started to lose power. We couldn't even get it to go fast. We could only drive slowly. In this situation, is there something wrong with the car that we need to call for roadside assistance? Have any of you ever experienced this ? United Kingdom Q&A