well... ive been driving my SS-III (which i assume has the 3S-GE engine) for over a year and a half now, and only recently did i realise that the petrol cap says "ONLY HI-OCTANE FUEL"... and ive been using regular the entire time...

is that like... really bad?
is it worth changing to hi-oc from now on?

(ps. when i first got the car my japanese wasnt so good, so it took me a while to actually be able to read that warning so im only half a retard...)

'the cheap gas in Japan is the good stuff over here...

ok - that makes me feel a bit better.
so would you recommend me paying the extra 30cents a litre for the hi-octane?
(and if so - do i have to completely empty my current fuel to do so?)

Americans with the 5SFE and 7AFE can use 87 octane (R+M/2) which is about the same as 92 octane (RON) in Japan... which I'm pretty sure is your cheap stuff. I believe that the 3SGE is a higher compression engine so I wouldn't be suprised if you had to run mid-grade or higher fuel.

If you run a lower octane in a high compression engine your ecu will pull timing until the knock sensor stops sending a signal to the ecu. This will obviously result in a loss of power. You may be ok with the lower octane fuel but I'd suggest finding out exactly what your car requires and what is available in your area. If you can't find out just run the highest grade fuel available... better safe than sorry.

Your cheap stuff is the regular stuff in Japan. what you call cheap is actually high octane. If your going any higher than that, than you must be driving a Jet to work!

He is in Japan...

LOW - US 87(RON + MON /2) equals Japan's 92(RON)
MID - US 89(RON + MON /2) equals Japan's 94(RON)
HIGH - US 91(RON + MON /2) equals Japan's 96(RON)

when you say "equals, do you mean that its the same...
meaning that Japans 92 is the same fuel as the low octane US fuel?
if so, that makes japanese fuel pretty bad...

All these points are true, however i am driving a Japanese Celica, which was designed in Japan for Japanese fuel, and so regardless of how US fuels compare, im wondering if im doing serious damage to my car by only using regular Japanese fuel instead of hi-octane.

And if, after 1 and a half years driving with regular, the damage already done is unrepariable, and so i might aswell just continue with regular fuel...
or on the other hand, would changing to hi-octane remedy any problems and improve the engine working back to its best state...

not the clearest of posts, but i hope someone understands

Yup. Pretty much the same. It's just rated differently.

My first post pretty much explains what happens when you run a lower octane fuel. It can cause damage but the knock sensor does it's best to prevent that. If you run the higher octane fuel, your ECU will restore the timing back to where it's supposed to be and you'll probably see an increase in performance... that is, if the knock sensor did it's job.

I see your point. I guess ill start using hi-octane (theres only three types of fuel in most gas stations around here, diesel, regular and hi-octane) since its only an extra 10cents a litre.

As for whether the hi-oc is 94 or 96, i have no idea, and i would hope that all gas stations around my area use the same type, since i guess mixing them wouldnt be too good? Its all pretty confusing since i am pretty much a newbie driving a celica cos i "loved the design".

Dare i embarrass myself even more and ask what the hell 'knock' is?!
i'll go read up on the forums

thanks for all your help though, you're a patient lot even with newbies like myself