Regular gas
It's just called smart bcuz it uses less gas cuz it's smaller
The 2008 Smart Fortwo runs on premium unleaded (required).
The 2010 Smart Fortwo runs on premium unleaded (required).
The 2014 Smart Fortwo runs on premium unleaded (recommended).
The 2012 Smart Fortwo runs on premium unleaded (recommended).
The 2011 Smart Fortwo runs on premium unleaded (required).
The 2009 Smart Fortwo runs on premium unleaded (required).
The 2013 Smart Fortwo runs on premium unleaded (recommended).
An energy efficient car can use gasoline, diesel, CNG, or electricity as a fuel.
Electricity, Hence the name "electric car"...
Yes, you can use unleaded fuel even if your car calls for super unleaded fuel. These are essentially the same kind of fuel so it will not mess up the performance of your car.
Replacing a fuel pump is a very time consuming difficult job it would not be smart to install a used fuel pump from another car. You just may end up doing it again a a few months. Install a new fuel pump.
The fuel a solar car uses is energy from the sun converted into electricity using solar cells.