We put on a set of the "ECO" mud flaps, the ones that are not solid but allow air to pass through them. We ran a load over the past 3 days, Ohio to CA. It was a very light load, 8lbs, so it may not be the best test but it seams that it has a pretty big affect on you MPG. We had been running in the 9.8 -10.3 range most of the time including reefer loads. On this load we averaged 10.6mpg. The range was 10.2 - 11.03. That included all the mountians and some areas with high winds. We will continue to watch the milage and hope that this is a real trend. Layoutshooter