Tips for staying strong and healthy. I often wondered what the secret is of an elder in their 80's who is strong' still drives.

You’re right, seeing someone who is really fit, active, sharp and engaged up to a high age really makes one wonder what their secret is. It turns out though, that at least part of this is not as much of a secret as it might seem. As my grandma used to say, becoming a graceful old lady starts when you are in your twenties. Given the latest research on the topic, my grandma seemed to have been right to some extent: having healthy habits all through your life pay off. Research has also shown though, that it is never too late to introduce some of those habits in later life, and still see benefits. Unfortunately there is no magical supplement or single exercise for this, even though a generally healthy diet and vitamins are never wrong. The one big thing we seem to have learned though is that staying physically active, especially when combined with a social activity, actually not only increases physical but also mental health! It also helps to keep our strength and mental sharpness longer.
It sounds like you are worried that your mom is getting weaker and that she might lose, or has lost her ability to drive and her independence. This can be both frightening and frustrating. Without knowing more about her situation and assuming that she does not have any serious health conditions, here are some general thoughts of things you could do. For example, taking your mom for walks, including her in your family life, and encouraging her to keep doing things on her own (all if possible) would be good strategies to start with. Whatever you plan on doing though, one of the key things is to involve your mom in the process! How is she feeling about this? It has been shown that persons which feel to have more control over their lives and aging process age more healthy. So ask her what she might like to do in terms of physical activity, and this can come in many ways. What is she good at, what has she enjoyed doing in her life? Encourage her to take part in social activities that SHE might like. Also, you could tell her that we can get back brain matter when we try new activities and are engaged with other people, even when not as physically healthy as she used to be. Volunteering activities seem to be especially beneficial. It might be good to get information about courses, clubs, programs and other resources that might be available for elders where she is living. If she still lives alone, maybe she has friends her age that still drive and that would like to join a club or take a course at a nearby community center with her. I hope this helped a little and gave you some ideas!

There are many factors. First and foremost is good genes!