Octane Level

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Well, the octane number that I run won't be of much help as the octane standard used here is the average of research octane and motor octane. I run the mid grade available in my car. Octane is a balancing act.... but I'm not going to get into that.

95RON is what Toyota recommends for the MKIII GTE at sea level. 97RON is the recommendation for the GE at sea level. Higher octane fuels allow the ECU to increase the timing advance resulting in more power; However, you may notice worse mileage as higher octane fuels contain less kinetic energy.

At higher altitudes and in colder climates you may run lower octane rated fuels as the potential for detonation deminishes in proportion to these.



This is from the MKIII owner's manual:

Originally Posted by UK Toyota Supra MKIII Owner's manual

7M-GTE engine:
For optimum engine performance. Toyota recommends using premium type gasoline with an
octane number of 95 or higher (Research Octane Number).
However, if such premium type cannot be obtained, you may use gasoline with an octane number as
low as 91.

7M-GE engine:
Select the octane number of 97 or higher (Research Octane Number).

NOTE: The numbers above are RON only! The US and other markets use different methods of determining octane rating: Motor Octane Number and/or Research Octane Number. The US uses (MON+RON)/2... this number is almost always lower than RON by itself.