He has driven since he was sixteen, he will tell you he has never caused an accident, and there is a scrape on the passenger door that nobody can explain. Taking the keys is not one talk but a transition, and how you run it decides whether he loses only the car or the car and his trust in you.
Before you say one word about the car, notice what is rising in you, whether it is dread about the next scrape or anger that he will not hear you. That is yours, it is normal, and it is worth one breath before you start.
Before you read his driving as a fight you have to win, rule out what an appointment can fix, since vision, hearing, and medication all sit upstream of the wheel. New glasses, a hearing aid, or stopping a sedating medicine (Ativan, Tylenol PM, some allergy pills) can genuinely improve driving for a time.
When he insists he can still drive, he is not lying, and he is not in ordinary denial either. Dementia can damage the brain's ability to notice its own decline, a condition called anosognosia, which means the disease has taken the gauge a driver uses to judge himself. That is why showing him the dent goes nowhere, since the argument is being delivered to equipment the disease has already impaired. He looks at fifty years behind the wheel and sees a good driver, and inside his experience, that is the truth.
Your observation counts for more than his confidence. Clinical guidance treats a family member's rating of the driving as marginal or unsafe as real evidence of risk, while the driver's rating of himself tells the doctor almost nothing.
Watch also for the changes he has made without announcing them. Driving less, staying off the highway, and avoiding night trips can look like reassurance, but they are the disease compensating, and they usually mark the stretch where risk is rising. A diagnosis alone is not the verdict, and it is not a pass either: some people in the mild stage can still drive safely for a time, and every progressive dementia eventually ends driving. The honest way through that uncertainty is an evaluation and a plan, not another kitchen-table argument.
Print the one-page log if you want somewhere to keep this, and take it to the appointment.
This is what the tracking is for. A dated log of drifts, dents, and wrong turns turns your worry into something a doctor and the DMV can act on.
He may lose the car and still keep you, and that is the outcome to measure this by. The verdict can come from the doctor, the evaluator, or the state. The rides and the reassurance come from you.