An 80 year old bloke marries this beautiful 20 year old woman.
About 9 months later they turn up the hospital maternity section.
His wife gives birth to a beautiful little fair skinned boy.
The nurse says to him "That's amazing at your age".
He replies "Well, gotta keep the engine running".
A year passes and they turn up at the same hospital again.
Same result - a beautiful fair skinned boy.
The same nurse again says how amazing he is for 80.
Again the old guy replies "Gotta keep my engine running".
Well, another year passes, another hospital trip, same nurse.
She brings the 3rd little baby out for him to see.
"Yep, I know" he says "Amazing - but I'm still keeping my engine running eh?"
The nurse replies
"You might want to change the oil - this one's black..."