Miricle oil additive?

[John Larson]

Brandon asked: "Alright, so is there a miricle (sic) oil additive I can 
count on extending the life of my Porsche flat 6? Prolong, duralube, slick 
50? I never used the zmax but have used various others in some of my cars 
over the years. Which is best in others opinions?
My car is running long on miles and even though it's an sc and reliable, I 
don't like the thought of putting 5 figures into it."

And John answers:  No.  All the products you mention are "snake oil", and 
all the manufacturers of them are either under indictment or injunction for 
fraud.  Slick 50 was the first to go (several years ago), and Zmax went 
under in the past few weeks.  There is NO product, either on or off the 
market, that will do what you ask.  If there were, car manufacturers would 
be all over it!  Use top quality oil, filters, and tune up parts, perform 
maintenance as required, and find a shop that cares as much about your car 
as you do.  I have customers in the 500K mile range with their 911SCs, and I 
know what they're capable of when properly cared for.