Over the years 100s of ideals to increase milage have been postulated. The failure rate seems to be almost 100%. What really has me going on this one is it's almost april the first and pretty well will be when the results are posted. I believe a percentage of us keep an open mind and personally hope there is a signifigant upside. After driving and watching for forty five years my beliefs at present are synthetic oil improves milage to some degree and a spark enhancing device promoted years ago still has a home on one of my old gas mercedes. But time will tell even if I am somewhat cynical at present. Oh yes spending the time to keep an engine tuned up properly seems to have always been of benifit. Not snake oil but takes effort and will maximize milage.