Synthetic Oil

[BailOut]

Originally Posted by Kaotic Lazagna

hmmm, now you have me worried, but then again, Black Yaris said that the Prius comes with that weight and viscosity oil.

Never confuse the engine in the Yaris with the one in the Prius. Even though they have the same designation (1NZ-FE) there are 2 major differences between them:

1) The Prius' ECU runs the engine in an Atkins cycle which involves a longer spark at a lower temperature (for ionization) and requires less fuel as it burns more thoroughly but at a lower RPM/torque level. The Yaris' ECU runs the engine in a typical Otto configuration which involves a short and hot spark at the top of the compression stroke. This means the Yaris' engine runs at higher RPM and hotter.

2) The Prius' engine is almost never in a direct wheel feed scenario. The engine feeds to the HSD and the battery (which in turn runs the electric motor), and the HSD plays a hardcore game of matching inputs from both the engine and motor to produce torque in the CVT. The CVT in turn plays a hardcore game of balancing torque input and output to produce movement. These systems are a far cry from the Yaris' direct feed to either a transmission (MT) or torque converter (AT) which immediately convert torque to wheel drive.


The point of all of this is that the Prius' engine only receives about 1/3 the beating that the Yaris' does. As such you can get away with a lighter oil in the Prius than you can in the Yaris.

As with most other things sticking to the manufacturer's recommendations is best, and Toyota says 5W-30 for the Yaris.