Since 1.Jannuar 2011 are available at filling stations petrol fuel E10. These have a 10% blend of ethanol (previously 5% max.).
PRINCIPLE is a distinction between Webasto heaters - retrofit or original equipment

Aftermarket:
Cars - - Here are the following Webasto heaters since the introduction of the Thermo-Top C from (1997) compatible. Thermo Top C, E, P, V
Thermo Top Evo 4, 5 and 5 +

OEM:
It applies only to information provided by the vehicle manufacturer

The use of ethanol is due to the limited energy budget, reduced heat output result.
Source: Webasto