I hear on this and other forums about people changing from dino engine and tranny oils to synthetics and reporting 2-3 MPG increases, or even more. Often, this is with the synths. having similar viscosities. I don't think Mfrs. would pass this up, and not put full synthetics in all the cars they make, if this could be true. It seems that they spend millions to get a few tenths of a percent increase. The only mileage/power gains I have really felt or measured were when going to a thinner viscosity [concerning lubes]. What do you guys objectively conclude?