Trevor

First off Xb's only need 87 octane. They should never be damaged on 87 regardless of weather or engine load. I think the conversation has turned from what they need into what they can put to good use.

You know...there's alot of people making assumptions on here and regurgitating what they've read. It really depends on how Toyota engineers programmed the computer. Who knows if they built & locked the timing maps around 87 octane ONLY or if they allow the computer to advance timing based on fuel quality which should allow for a couple extra HP. I'm pretty sure none of you have the inside information to know for sure. Two ways to find out though. Obvious one is to dyno at the end of a tank of each fuel you're trying to test. The other way would be to get an OBDII datalogger and log timing Vs. RPM on a 3rd gear pull on the different fuels. If you get more timing advance with the 89 then you're almost certain to be making more power. Not much more but more just the same. I have an OBDII datalogger for Japanese cars but this just hasn't been important enough to test out.

Sciond

like I said test it

mgithens

Trevor is making total sense.. I for one would like to know where to look for my "fuel quality sensor"...

and to throw in the info... we have 85/87/91 here in Colorado... and 85 is overkill because WE HAVE NO FREAKIN' AIR....

octane is not a measure of power, it is a measure of stability... PERIOD... go read the gas faq... it is listed in the links section...

chino5149

I 2nd that. At least that's how it was in my old CRX. I'll haven't tested the Scion to find out if it's the same. But a couple years ago I took price per gallon, mileage per octane achieved. And it turned out being cheaper using super (went father per dollar). And the super makes your ride a lil pep-er as well. And with super+octane booster I could actually feel a difference in power. But that was in a swapped CRX. Other cars may react a lil differently though. And for who ever said super or higher octane will make your car run worse, you need to do a lil more research.

icemilkcoffee

I don't know where your 'theory' came from but it is totally wrong. Using a higher octane gas than the mfg calls for will do NOTHING for your power. If you use a lower octane than the mfg calls for you'll lose power- that is true.

Bottom line- use whatever gas the mfg tells you to. In this case 87. End of debate.

Sciond

no you need to research if you understand obdII systems

TheScionicMan

http://auto.howstuffworks.com/question90.htm

Trevor

So those of you that are still saying 87 octane only...how do you know for certain that the computer isn't programmed to add any extra timing on higher octane fuel? Have you tested it on a dyno or with a datalogger?

Companies either reccomend regular or premium fuel (with very few exceptions (See the new EVO requiring 93). Manufacturers avoid requiring premium fuel because that can put a dampner on sales for all but the people that don't mind spending some extra money on performance. On cheap cars like the Xb that can especially hold true. Just because the engineers programmed the engine management to run safely on regular gas does not mean that they didn't set it up to advance timing when higher octane fuel is introduced. Example? My old 98 BMW M3. It required premium fuel which is 91 octane by definition. I live and race at 3,075' altitude and we used to have 93 octane locally. With 93 it went 94.3 MPH trap speeds in the 1/4. After 93 octane dried up and the switch to 91 trap speeds dropped to 92.4 MPH. With 100 octane fuel in the tank many people on the BMW boards have picked up 1.0-1.5 MPH over 93-94 octane in practically bone stock cars. It's well documented that the E36 and newer M3's continue to gain power from 91 to 97 octane. Above that returns dry up. But there you go. 91 octane gets you bottom of the barrel timing advance but the car still runs safely with it. The problem is power is not all it could be since the computer is just doing its best to keep knock at bay and the engine safe. Add better gas and that particular ECM is programmed to continue advancing ignition timing up to the edge of detonation or until the pre-set max is reached which is usually hit around 96-97 octane. The question still remains of how the computer is programmed in the Xb. You may be right...it may not advance timing past 87 octane levels...but until somebody actually tests it out in a semi-scientific way you can't say that for certain.

Let me say it again though...nobody needs to put anything other than regular gas in your Xb. The car should never have a problem with it.

Sciond

like I said it may make it run worse and to test it

LeBeastMan

My box has only used super (CA 91 octane) since day 1, and has had no problem, nor do I see a lack of perfomance, I also have driven a box that only has had 87 octane since purchased and notice no difference.

My .02

MotoMan_YZ400

see i use Cam II purple, 114 Oct. Help keep from detinating w/ my 15:1 compression ratio. :-P nothing like $5 a gal.

mgithens

I will be running an OBDII analyzer full time in just a few short weeks... I will report back my findings... I will eat the WASTED 20 cents/gallon for a tank or two to show what the system is running...

here's an example of what I am referring to...
http://obddiagnostics.com/

it's 38 degrees outside and my hands are about to fall off from installing my new XMDirect...

J_A_Trevino

93

CBSIMONSEZ

Speak for yourself ...... This comment directly from the SPED!

dgHotLava

for myself huh....i am required to use super now.

cosmo93940

cosmo93940

dgHotLava

i think you got a little mixed up there cosmo.

(he said thanks for the input in the subject)

no prob...

Sciond

thanks :D I am curious

kacosta

use the cheapest gas you can find the engine was designed
to run on 87 it runs better on 87 you can use whaterver you feel is best for your climate and operateing conditions for me
in the north west and when i lived in ca i have allways used 87 i am a technician of 17 years (toyota/lexus/acura) i never had any problems with 87 with any of my cars

empleh

i think the point of all this is that using anything but 87 is pretty much just a waste of money. if you got 1mpg better, and save 10 miles per tank, at 1.80 a tank, you're saving $0.60. but, you're paying $0.10 more a gallon, which is a dollar for 10 gallons. which means by putting 89, you're not cleaning your engine any better, but paying $0.40 more for performance that you can't feel. i think i'll stick with my 87. just make sure you fill up at chevron or 76