Not noticed any appreciable change in FE from my 2013 ZenN 50 cc-honestly i'm not sure if it's because I keep Boat Gas (93 Octane 0% Ethanol) in the tank or because I only have a 0.75 quart oil resevoir (fast heating as a result). Then again, the 1.2 gallon tank might not be large enough to show the tablespoon or so difference. :P
At any rate, 130 MPG, slightly variable(extra cargo, old vs new oil etc) whether hot or cold.
The one exception is the rare occasion that we have ice/snow in Coastal NC. Little Wing does not like the ice
one bit. In those rare periods her FE shoots through the roof-because I will carpool instead.
