I have a 2000 Nissan Maxima. I oil change it regularly with the recommended oil weight. It is used as a driving school car and has about 210,000 miles on it. I replaced the ignition coils and spark plugs some time ago, maybe 30,000 miles ago. When I drive the car the car has trouble going faster than 40mph and when I hit the gas it revs at around 3500rpm before it gets anywhere but the speed climbs very slowly. Also, when the transmission changes gears (VCDS 15.7 automatic) the car kinda jerks. All the fluids are good and topped off regularly. The motor is also pretty loud but that s old news. Sometimes the car overheats and shuts off. I replaced the radiator (around 130,000 miles) and thermostat(180,000 miles). Can anyone tell me what the problem could be? Any advice is appreciated. Thank you.