The chances of your car dying a premature death because you didn’t use any oil additives are so slim, I wouldn’t worry about it. How often you change your oil and whether you use the proper oil are a much bigger factors.
It is much more likely your automatic transmission will fail before your engine. If you are looking for a way to extend the life of your car, I would say most people know to change the oil on a regular basis, so I would look at the cooling system and the transmission. Having the coolant changed every two years and having your transmission properly serviced every 30,000 miles could help your cars last longer. If you have an automatic transmission, that would mean draining the fluid, dropping the pan, and cleaning the filter, not just draining and refilling, and not having the fluid flushed.