Toyota prius Owner's Manual page 582

6-1. Specifications
 Engine oil selection
"Toyota Genuine Motor Oil" is used in your Toyota vehicle. Toyota
recommends the use of approved "Toyota Genuine Motor Oil".
Another motor oil of matching quality can also be used.
Oil grade:
0W-20, 5W-20, 5W-30 and 10W-30:
API grade SL "Energy-Conserving", SM "Energy-Conserving" or SN
"Resource-Conserving"; or ILSAC multigrade engine oil
15W-40 and 20W-50:
API grade SL, SM or SN multigrade engine oil
Recommended viscosity (SAE):
Temperature range anticipated before
next oil change
582
PRIUS_OM_OM47871E_(EE)
SAE 0W-20 is filled into your
Toyota vehicle at manufacturing,
Preferred
and the best choice for good fuel
economy and good starting in
cold weather.
If SAE 0W-20 oil is not available,
SAE 5W-30 oil may be used.
However, it should be replaced
with SAE 0W-20 at the next oil
change.
If you use SAE 10W-30 or a
higher viscosity engine oil in
extremely low temperatures, the
engine may become difficult to
start, so SAE 0W-20, 5W-20 or
5W-30 engine oil is recom-
mended.