Answer by Thomas Zerbarini:
MoGas is motor vehicle gas or gasoline. General Aviation aircraft owners sometimes use MoGas instead of AvGas to save money. MoGas generally is cheaper than AvGas. Pilots flying experimental aircraft tend to use MoGas more than pilots flying manufactured aircraft.
There are issues that must be considered if using MoGas.
Also, check out the FAA Advisory Circular on using MoGas:
MoGas may become a more popular form of fuel for General Aviation due to the fact that AvGas may become obsolete over the years. Aircraft engine manufacturers are already addressing the issue by making duel fuel engines.