Which octane is best for the 3S-FE engine? Options

[Authentic]

Hey everyone,

So I've been on this forum for a little while now and I've figured solutions to most of my questions from seeing previous threads, however I couldn't get the search to work for this particular question I have.

So for the people with the 3S-FE engine, I was wondering which octane you run. I have been using 91 since I bought the car in November, and my Dad said that he ran our old 5th Gen Celica GT-R (3S-GE I think) on 91 also, however I decided to try 95 today since I was driving on the fuel light. I had a short drive home from the petrol station so I haven't had chance to see any difference yet.

So yeah, let me know which you use and feel free to yell at me if I've done something wrong, cheers.

[Galcobar]

Make sure you're talking about the same scale when discussing octane.

North American pumps display octane rating based upon (R+M)/2), which is the average between the Research Octane Number and the Motor Octane Number. Japan, Europe and Australia use the RON alone -- New Zealand uses RON. The same gas rated in RON would have a number 4 or 5 higher than on rated in (R+M)/2 -- so "regular" New Zealand 91-92 octane would be the equivalent of "regular" 87 in North America.

That difference is the source of a lot of confusion, especially since many Japanese engines do need gas with higher octane values. It's conflated though with engines which use the same fuel, but appear to have different octane needs because the fuel is labelled differently. If it's the same engine, it'll use the same fuel (certain high-performance exceptions exist but they're rare).

The 3SFE, like its successor the 5SFE, is an economy-oriented engine and runs on "regular" fuel, which in Japan/New Zealand would be 91 octane (same as 87 octane in North America). The 3SGE and 3SGTE are performance-oriented engines with higher compression ratios (11.0 and 10.3:1 versus the 3SFE's 9.5:1 or the 5SFE's 8.5:1) and therefore need the higher octane values in premium gas.

This post has been edited by Galcobar: Mar 2, 2012 - 3:19 AM