Premium Gas

[BailOut]

Originally Posted by Edd

The higher the number, the better. There is no damage from going to a higher octane level - you are just putting in purer fuel.

Octane is not a measurement of caloric content or burn-ability (cetane). It is a measurement of how high a temperature is needed in order to ignite the fuel. This is why premium fuel is usually only required on high performance engines (because they run at higher compression levels which generates more heat).

Higher octane fuel is actually less pure because of the extra additives which are used to make the fuel ignite at a higher temperature. These additives are also why it costs more.

Running fuel of an octane higher than what your engine is designed for can help with knock (detonation) but that is generally where the benefits stop. The detriments are:

- Fouled spark plugs due to the deposits left via incomplete burning.
- Greatly increased emissions due to incomplete burning.
- Fouled O2 sensors due to these emissions.
- Fouled catalytic converter due to these emissions.

Stick to what your engine is rated for. The 1NZ-FE engine in the Yaris is designed for 87 octane gasoline.