Keep your engine running

An 80 year old man meets his friends and tells them he is going to get married to a 25 year old woman.
“Are you up to it?” They all ask him.
“Keep your engine running” he says “You have got to keep your engine running”
A year later he takes his wife into hospital for the birth of a child.
The doctor says it is amazing for a man of his age.
“Keep your engine running” he says “You have got to keep your engine running”
Another year goes past and the wife gives birth to another child.
“Keep your engine running” he says “You have got to keep your engine running”

The doctor replies, “Maybe you should get the oil changed. Your new baby is black”