I use synthetics, typically Mobil 1, in my 4R and my wife's 3.2CL Type S.

On the other hand, I put whatever was on sale in the Xterra I drove for 11 years and never had any kind of engine issue.

I suspect the large majority of oils you can buy today, even SuperTech or whatever at Walmart, are good enough to ensure long engine life, but who knows? I did some research on high-mileage oils and the consensus seemed to be that they're unnecessary unless you're having any of the issues they're designed to address. Is there anything to suggest preventive properties that would merit using them before a problem exists?

My issue with all of it is whether there's science in play or just good marketing that steers people toward doing something about (and spending more $$ on) problems they don't even have.

Thoughts?