NHTSA Complaint #11532971 — 2016 VOLVO XC90

for last 2 years, my 2016 xc90 has kept request to add oil every 1 or 2 month. In May, 2023, my car speed suddenly reduced the speed to 25 miles and the turtle sign popped up. It was very dangerous when I drove it on the highway, it was almost get hit by the car after me. After I sent to dealer, I was told that the the cylinder of the engine did not work. The engine light has been on and off many times. I sent my car to the dealer regularly for the maintenance