[MetroMPG]

Pete: the one study I've seen which purported to scientifically demonstrate the MPG benefit of synth gear oils was done on large trucks. I just can't find it now and threw out those other two links instead after a quick search.

Christ: agreed. Those pages use weasel words talking about synth gear oils.

But by comparison, I don't think you will find the equivalent weasel words used by a major manufacturer about fuel economy benefits of synth vs. non-synth motor oil (of the same viscosity). Last time I checked, they simply don't make fuel economy claims for the motor oils. That says something to me.