i looked thru the search stuff quickly and didn't think i saw this anywhere on sl so i'm gonna ask it-i heard that when scion did the testing for the tc and came up with numbers such as hp, torque, etc that they did it with premium gasoline. supposedly it says that in the manual. did anyone happen to see it-i'm pretty sure that i never saw it in there although its supposed to be there somewhere.

 

hmm interesting never heard of it.

 

the only time higher anti-knock gasoline ratings will affect your numbers out of your engine is if your ECU is retarding the ignition timing to prevent pre-combustion (and no, I didn't google that I'm just good)

unless the compression ratio is high enough to pre-combust 87 octane gasoline (9.6:1 is hardly high compression) then you will see no benefit from running higher gasoline, and the owners manual tells you to run 87 octane for best results. If you should need higher octane then your manual would tell you to run it like every other car's manual that requires higher octane fuel.

 

in order to get more power from a higher octane rating is to advance the ignition timing, which btw isnt as easy as it used to be

 

Right, because if you are able to advance it mechanically, the ECU will just set it back to stock electronically.

Unless your car requires the use of premium fuel, there is no reason to use more than the recommended octane rating. Unless you modify the ECU or add forced induction premium gas will only make your wallet lighter.

 

yeah, higher octane won't do you any real good with a tc. and yes, it does say that in the manual in several places. i have the manual in electronic format and found it on 3 pages. here it is on one of them, copied/pasted:

page 132-
OCTANE RATING
Select Octane Rating 87 (Research Octane
Number 91) or higher.

 

in rare cases useing premium would cause damage to your engine because of the slow burning nature of premium gas the fuel will still be in the combustion stage as it exits your engine. When you use regular gas the engine makes a spark at TDC or somewhere around TDC, but with premium you have to create a spark earlier to take advantage of the slower burning gas thats why you advance the timing. You actually have to make a spark when the piston is still moving up in the compression stage.

I hope that made sense. i have to go to work now

 

"Research Octane" is a different number from what you see on the pump, hence 91 "Research Octane" is not premium gas.

Taken from Shell's website:
Look at any gas pump in the U.S. and you'll see this formula stuck there:
Octane = (R + M)/2

 

yeah, what jmiller20874 said.

 

nice. thx for the info guys

 

I think this is the number people try and quote for justification of using premium in the tC. Basically it's them not understanding what the two different numbers mean. Like pretty much everyone says, 87 is all you need to put in your tank. You won't mess it up with premium, but why waste the extra money if there is no direct benefit.

 

Research Octane number is the number used in Europe. My '71 VW bus also specifies 91 RON.

In the US, we use the average of the Research and Motor method octane number, This is referreed to as "(R+M)/2" The two methods are simply different test procedures using the same equipment.