Porsche 911 Carrera - Manual (Page 241)

the SAE class is given as a number and the letter
“W” (as in winter), for hot viscosity (measured at
212°F /100°C ) the SAE class is given only as a
number.
The viscosity of an oil is, therefore, always the
same if it has the same number of an SAE class.
Oils with two viscosities are called multigrade oils;
oils with only one viscosity are termed single-grade
oils.
Single-grade oils cannot be used in your engine.
The viscosity of the engine oil for your Porsche has
to be selected according to the ambient tempera-
ture given in the engine oil recommendation table.
Maintenance, Car Care
239