Jackd,
Again, you hit the mark. If Synthetics actually provide a 10% increase in fuel economy then don't you think this story would be on the back on every bottle and possible lead to govmt regulations that mandate the use of synthetics. Imagine if our country could change to use 10% less fossil fuel. Even a 2% drop in usage would have an incredible effect on the ecomomy.

In any case, my car seems to run better and rev smoother when it's clean.... I'm serious. But I know that this is just my own perception that results from an external appearance.

It would be nice to line up ten cars, five dino, five synthetic, all the same mileage and same model. The experts that can feel the difference would then be able to drive all the cars and tell us.