scionboi06

if one was to read the manual its says page 236 (2006) unleaded gasoline, Octane Rating 87 (Research octane number 91) or higher. what this means is that our cars can run on 87octane but 91 is ideal and higher is preference. ummm research that's the keyword.... but either way it comes down to environmentals and personal choice.

ack154

iTrader: (7)

It does not mean 91 is ideal...

Check here:
https://www.scionlife.com/forums/viewtopic.php?t=76399

(for those playing at home, in the 2005 manual, this info is on page 234)

Mouse

Bro.... thank you for posting that ^^......that is exactly the point. I am and have always been religious about my gas mileage and what brand I go with. And I am living proof having done my homework for many moons...(thats many years to noobs lol) ...
I stand by Shell gasoline's. I always watch my fuel consumption down to the mile... and I literally have consistently gotten on average 30+ mpg more than going with other suppliers. And that means a lot especially at the high altitude I live and drive at. And they put cleaning agents in their fuel to help minimize buildup...especially on the valves.
That's my 2 cents...but for me averaging 30-40 more miles out of every tank more than pays for itself in the cost per gallon and running the 91 octane.

Mouse

oh and just FYI... depending on your lo-cal in the nation... Shell is the only brand that I have seen that in the winter months when all the other brands throw buttloads of ethanol in their fuels... If you run 91 Octane Shell does NOT put any ethanol in that grade of fuel...which will give you better mileage for your buck than any other brand in the winter hands down.

scionboi06

and thats my point!

Windu

The thing with octane comes down to ignition timing. Higher octane fuel allows the ecu to run more timing especially in cruise situations. The higher the octane the more resistant to detonation it is. Theoretically this makes for better fuel milage by making for a more complete burn and maximises the power output of every BTU the fuel provides. Most factory tunes keep the timing just below the point of detonation via the knock sensor. This is the theory behind the vaccuum advance canister in distrubutors since the 40's. These old school setups will pull up to 60 degrees to timing in high vaccuum situations( ie part throttle cruise) to help with fuel milage.

Mouse

^^ and its not just what you mentioned...which is true...but also that at that higher octane... it is a CLEANER burn...and a more complete burn....which helps the internals in the long run by helping keep them more free of things like carbon buildup.

Windu

Very true.

Mouse

Windu... hey dude... we're in the same neck of the woods... let me know if you care to roll down to Scinergy meets for the Scion club in Denver some time... feel free to PM me if you want to.

scionboi06

Back home i ran 91 all the time, now in Atlanta i only run 93 my gas mileage is above normal power is flowing in all weather conditions, oh! and No one here on this little web site is a Authority on anything that i own. nor i to your possessions so choose what you like but don't be hell bent on your own offense its really not that serious. your opinion is not religion or WORD. lol!

Mouse

^^ oh you dirty bugger.... lmao... what I meant was to each their own...but I know I check that all the time for me...and know it works best for me....but for that brand of fuel and a couple extra pennies a gallon...it is a win - win situation for me... so was just passing on what I've learned over the past several years of trial and error.

ack154

iTrader: (7)

You guys can swear up and down all you want about running something higher... until I actually see any definitive proof that a higher octane is better for our car, I'll stick to what the manual recommends.

Windu

Yeah, its all theoretical. To each his own.

SquallLHeart

i dunno about proof of higher octane being better..

but i've seen more than once that it performs worse.. and it wasn't just me either... a few friends have tried it.

vettereddie

Just a quick question, why does 91 burn cleaner? I was going to post this earlier but got lazy with the typing.

When you get to the root definition of octane rating, it is NOT a rating of the fuel's resistance to detonation. Octane is the rate of burn, or how long it takes the fuel to be consumed in the cylinder. The lower the number, the QUICKER the burn. Detonation comes in because, with a lower octane fuel, it is more volitile, and prone to self-ignition due to hot spots in the combustion chamber, especially in higher compression (n/a) or boosted application. These secondary ignition spots radiate a shockwave outward, and when it meets the wave front fron the spark plug ignition point, you get knock.

With a faster burn rate, would you not get a more complete and cleaner burn?

For maximum performance, you would want to run the LOWEST octane fuel you can without causing knock or detonation. Race fuel is 106 because at their compression levels, anything less and the motor goes boom.

You get worse performance from 87 depending on vehicle because if it causes knock and the sensor picks it up, the ECU will pull back your timing, causeing a power loss. If you can run 87 without knock, it will perform better.

As for additives, does anyone have detergant information, if there is actually a greater degree of cleaning agents in the higher octane or do they all clean the same?

CarbonXe

iTrader: (1)

lol@people using 93 in a stock tC.

KrazyTc

From my personal experience. I have felt my car to run smoother with 93 and get a little more miles out of my tank, compared to running 87. But i havent studied it to the point that im sticking to one brand of fuel or anything like that. Im just saying thats what i experience with my car. I have been using 93 since my Spec V(04). And yes my Spev recomended premiun fuel. And i really could tell the diffrence on idle between the octane readings in my specv.

ack154

iTrader: (7)

That is a 100% different scenario than with the tC. That vehicle recommended the premium so I would expect there to be at least a tiny difference in performance/mileage.

You're welcome to run higher in the tC, but I assure you, there is no benefit. If there were, they would have recommended it like your SpecV did.

emptystreets130

I don't see how people cannot understand this. It all comes down to timing and control. You have knock sensor that tells it to advance or retard the timing to prevent pinging regardless of what octane fuel your are using. To the GS deal on the first page, putting regular in a vehicle that requires premium will not hurt the engine itself. It could hurt performance but that is because the timing it retard/advance to prevent it from doing damage. You're not going to feel that extra 5-10hp from using higher grades.

But like most people say, its all preference. If you like to spend more money on higher grade fuel then by all means, go ahead. It won't help the economy or anything. The feeling and seeing mileage increase is all in your head and is influences by a bunch of external factors (roads, tires, temp, condition of engine, wind, weight.......)

ElevationTC

When i was stock i used to run 93. 60k miles on the motor always changed with mobile 1 5w30...

Ive been on NO2, Supercharged And now boosted on a custom kit with 340WHP..


Not saying its helped but i always have and had no problems with my motor...

Also When i did use 93 on stock motor.. I got better MPG. so it let me to believe that it was better for my motor! IMO run what you want...

I doubt that running 93 or 87 is going to really end up making a diff in your car!