When I first got my Robins/Suburu motor new in mid August I was getting around 138 mpg. 2200 miles later I seem to getting around 114 mpg. I have a Robins/Subura eho53 friction drive system on my cruiser. I have run unleaded regular in it. Performance is good. I change oil around every 3-400 miles with Mobile 1. I have run some Seafoam thru it in case of some carbon buildup. Any ideas? Thanks.