SMART Fortwo coupe Operator's Manual page 226

Service fluids and capacities
224
vehicle: MB 325.0 Anticorrosion/
Antifreeze agent.
Before the start of the winter season (or
once a year in hot southern regions), you
should have the anticorrosion/antifreeze
concentration checked.
The coolant is also regularly checked each
time you bring your vehicle to an
authorized smart center for service.
Anticorrosion/antifreeze quantity:
Approximate freeze protection
-35¦ (-37¥) -49¦ (-45¥)
Cooling system 2.27 US qt (2.15 l) 2.50 US qt (2.37 l)