If you care about your care, you change your oil every few thousand miles. This mechanic shows what a filter looks like if you don’t change it for 50,000 miles:
In order to keep our own engines running, I believe that our cells are kept young by mechanisms that can be optimized- both preservation and destruction (with replacement). Our body doesn’t go in for a total flush so it is more like having the oil continuously exchanged as it becomes sludgy from the accumulation of damaged stem cells that results from replicative senescence. It is more like maintaining a swimming pool with clean water.
To change analogies a third time, the pool of cells that you use are like the water in this container.
In order to fill the container, you have to drain the container. Likewise, we are always bathed in excess stem cells which is why stem cell therapy doesn’t help unless you also kill off the dysfunctional ones that are occupying the current kingdoms.
So optimal health relies upon draining the bad, sludgy cells (which occurs from toxic and replicative senescence) and replacement with factory fresh cells from the mesenchymal stem cell pool.