Octane information for those who might not know

[StreetBrawler89]

I currently run 93 octane gas in the 08 Tc, but i recently learned that doing so can cause the ECU to believe its running rich and dial down the injectors causing to run lean, last i heard running lean(to a certain point) helps create power. So in the end the questions is this, is it bad that im using 93 octane?

[navylife59]

Waste of money as the ECM is tuned for 87 Octane. The ECM is always trying to keep the Stoimetric AFR, so yes it does alter things slightly. The only way that your going to see any performance gain on a stock NA motor is perhaps in an extremely hot environment. The 93 Octane would allow the ignition timing to advance more before detonation.

[StreetBrawler89]

I plan to grab up a forced induction unit and I know thats going to increase the minimum octane, does it depend on what turbo I get or the tuning and inginition timing? Thanks for your help, I know a little about alot, but im still learning the more advanced stuff.

[navylife59]

All of the above can affect the level of Octane needed to make power and prevent detonation. Adding some form of intercooling will allow more bang for the Octane. Even the ambient temperature levels in your environment can affect the amount of Octane needed to prevent detonation.

[navylife59]

Not just Moderators have the power to resurrect old threads, you can too.

I came across this good bit of information in the Public Domain from the State of Minnesota. It contains useful and straightforward information regarding gasoline Octane ratings.

http://www.state.mn.us/mn/externalDo...ctaneFacts.pdf

Here is a well written article concerning gasoline and it's modern derivatives.

http://stason.org/TULARC/vehicles/ga...faq/index.html

[2AZ-FESedan]

Just thought I'd share this if you look on the back of the owners manual it stated there that it runs on 87 but it can accept any octane up to 93 if you'd like for better performance. in so many words. I have a 2002 camry personally with obviously the same 2AZ in the scion and my owners manual says that. So officially according to toyota there is some benefit to be pulled from higher octane fuel than standard 87. Obviously on a car that would not state that there would be absolutely no benefit and could possibly bring undesired results.

[2AZ-FESedan]

Just thought I'd share this, I have a 2002 camry with the same 2AZ 2.4 that the scion offers. On the back of my owner's manual it stated that the car takes 87 octane but if you desire it can take any octane up to 93 with some performance benefit. It states it a little better than me, and says something along the lines that you can put up to 93 octane in the car and you will get some performance benefit in doing so. So for those who asked about it, Toyota claims the 2AZ-FE's can accept higher octane safely and with benefit. Obviously if it was a regular computer controlled car that didnt state that there would be absolutely no benefit and their possibly could be some problems caused from doing so.

[CadenceScion]

I'm going to agree w/ you on that. I have an o6 Scion tC and I refuse to use 87 octane because of the poor mileage I have gotten. I also don't get the get up and go using the 87 octane, its rather sluggish IMO. I have gotten on average of 31-33 MPG w/ 89 octane and every so often I'll throw in some 93 octane to clean the engine out w/ some good fuel injection cleaner. I also have a Scangauge II that sit right on top of my steering column that tells me what MPG's I'm getting, so I know for a fact the octane makes a difference. 87 octane doesn't burn clean enough IMO and there isn't enough cleaning agents as there is in higher grades of gas.

If the engine in your vehicle is 9:1 compression or higher 89 octane or higher is fine, 7-8:1 regular/87 octane is plenty. The higher the octane, the slower the burn. This means it burns more efficiently and cooler giving better performance and mileage. You look at the V-Tec H22 in a Honda Prelude, that engine recommends mid-grade/89 octane or higher which is a 4 cylinder. I would rather pay a few cents more per gallon for better gas mileage, better performance, a cleaner burning fuel and less carbon build-up. You look at an engine that has ran 87 octane all its life verses an engine that used 89 octane or higher and see how much cleaner the internals of the engine are. I get people all day long that tell me there really isn't that much difference between 87 and 89, and its not necessary. Pending on the manufacturer, age and how the cars computer is tuned or adjusts to the gas will differ. On average it takes 2-3 tanks of a higher octane fuel for the vehicles computer to readust. Also keeping in mind whether your buying a no name gasoline, top-tier gasoline and even E85/Ethenol will affect the gas mileage and performance as well.

[navylife59]

True. Big Brother Oil would be furious.

The only real world benefit would be slightly better MPG. The ECM is going to real back any gains unless you are in a very hot environment or charging your car hard as on the track. What it will do for sure over 87 Octane would keep the ECM from retarding ignition timing for knock.

[navylife59]

I am merging these similar threads. Higher Octane fuel has more energy potential so the higher the Octane, the more power potential that can be tuned and more MPG. Ethanol blended fuels burn cleaner with more available Oxygen than standard gasoline but at the cost of less energy potential and decreased MPG. E85 is more resistant to knock than 93 and even 100 Octane fuels so more ignition advance and boost can be utilized on F/I engines allowing them to make more power. The downfall to this is that it takes alot more fuel to make this happen.