When Mobil 1 first reached the market, we did the SOAP (Spectrographic
Oil Analysis Program) on our racing engines, and synthetic definitely
lasted longer according to the data. However, those engines subjected
lubricants to very high pressures and temperatures, apparently tolerated
better by synthetic than organic.

I think some aircraft engine makers/users have similar numbers.

The important question is whether the longer life, better protection,
and higher cost all balance out to a net savings. As I see it, if you're
driving a race car or an airplane, probably. But my Prius engine doesn't
get hot enough to hurt when I touch it at the end of a trip, and the oil
looks fresh even at changing time. In these cars, I don't think
synthetic will make a difference.

Ike