This proof comes from an Automotive Lubrication Engineer....
Finally, we asked a respected petroleum engineer why auto manufacturers
don't specify synthetic oils for used in their products. His response
was both candid and revealing: "Auto manufacturers must, by necessity,
stick to the 'generic' SAE standards in recommending oil grades and
viscosities...and synthetics are way ahead of SAE standards. The top
SAE motor oil classifications (SD, SE, SF, etc.), rather than being
benchmarks of excellence, are merely 'highest common denominators'. The
highest SAE rating (currently 'SF'), for example, is determined not for
the state-of-the-art performance of the better synthetics, but rather
for the best possible performance of petroleum oils *currently
achievable by a majority of petroleum oil producers* (emphasis ours).
It is not surprising then that synthetics pass these qualifications
effortlessly. What is needed is an entirely additional set of SAE
standards for synthetics. Such a grading system would, in effect, start
where current SAE (petroleum-oriented) specs leave off. If such a
premium grading system were adopted by the Society (SAE), then you'd see
the automakers universally recommending lighter oils in grades and with
recommended drain intervals completely beyond the reach of petroleum
products..."
This is the whole long article for the Ultimate of Proof of synthetic being best that lays all your questions to rest forever!!!! This is the Nail in the Petroleum Coffin!!!!
http://www.mr2.com/TEXT/synth_oil.txt