Toyota 2013 Prius Owner's Manual page 643

6-1. Specifications
Fuel information
You must only use unleaded gasoline in your vehicle.
Select octane rating 87 (Research Octane Number 91) or higher. Use
of unleaded gasoline with an octane rating lower than 87 may result
in engine knocking. Persistent knocking can lead to engine damage.
At minimum, the gasoline you use should meet the specifications
of ASTM D4814 in the U.S.A. and CGSB3.5-M93 in Canada.
Fuel tank opening for unleaded gasoline
■
To help prevent incorrect fueling, your vehicle has a fuel tank opening that
only accommodates the special nozzle on unleaded fuel pumps.
Gasoline quality
■
In very few cases, driveability problems may be caused by the brand of gas-
oline you are using. If driveability problems persist, try changing the brand of
gasoline. If this does not correct the problem, consult your Toyota dealer.
PRIUS PHV_OM_OM47787U_(U)
6
621