I've read several posts where people state that "synthetics" (implying all synthetics) get better gas mileage than comparable weight dino oils. Can anyone tell me where the source of this information comes from? I'm not saying that it's wrong, I just can't rationalize it in my head. My experience years ago when I switched between the two seemed to be the opposite. I read a post in the last few days of someone else that had similar comments. I'd be more inclined to believe it has to do with the level of friction modifiers in the oil, and that many synthetics have more than the dino oils. That implies that there is nothing inherent in G-III or G-IV oils that gives them a lower coefficient of friction (it wouldn't surprise me if G-V oils are different). I'm not looking for testimonials. I know there are lots of people that feel they're getting better fuel economy. I also know that there can be a placebo affect. That's why I'd like to see the facts.