#1. plug in a timing reader, and check what your timing is doing with each fuel. #2. the tc is not high compression, but my 07 civic is and it calls for 87 octane also. #3. i let time slips at the track determine, and 91 was not as responsive as 89 for me. #4. thiers a reason none of the scion og's are on this debate.

 

Not the same engine as ours, but I read somewhere that the honda accord actually picks up 10hp on 91 even though the factory recommends 87. As I recall it had something to do with the stock ecu advancing the timing until it senses knock. With the higher octane being more resistant to preignition the timing could be advanced further than when using 87 thus the hp gain. Maybe the tC ecu could respond in the same way?

 

this is why im looking to buy a monitor of a/f and timing. i want to see exactly what it does with each fuel.

 

If it did... don't you think someone would know by now and more people would be using higher grade? Or beyond that... if it were that easy to gain more power, do you think maybe it would be recommended from Toyota?

 

The ECU in the tC seems to try and keep the A/F in the range for best Emissions and Fuel Economy. My experience with Honda and GM ECUs, is that as stated before, they will advance timing until knock is detected and then will back off to maintain a predetermined safety margin.

 

I use 93 octane in my tc.... It's N/A part of the time ;)

 

Noticed no response difference in octane levels in my tC, but I definitely did in my first owned vehicle, 87 Jeep Cherokee. It ran extremely responsive and with much more power on 91+ octane.

 

Going between the "standard" different grades of gasoline fuels available to the masses in the U.S. .... there will be little if any actual hp gains from using a higher grade fuel. The main advantage from using a higher grade fuel is that it burns more completely than the lower grade fuels and have fewer contaminants so over time there will be less build-up of carbon deposits on internal engine parts (valves, etc.)
Another advantage that I've found gives me the best mileage is there are some fuel stations that do not put ethanol in their higher grade fuels. This does help with getting better mileage.

 

Did everyone miss the "or higher" part in the original post... gas is just a preference. Just my 2 cents.

I think what it's really trying to say is your car needs gas.

 

something also to consider a lot of gas stations have now started getting gas with 10% ethanol i know it doesnt sound like much but ethanol has been proven not to be good for engines, you get less mpg and is pointless so make sure when you get gas look for a small sign on the pump that says may contain 10% ethanol or less

 

i agree. just use 87 in your car. i used 87 forever, but now i'm using 91 only because of my turbo now

 

I am going to have disagree with some of you in here as far as this post goes. I own a 2006 Scion tC (Azure Pearl). I have owned my tC for 2 years now and use 89 octane. I found by running 87 octane in my tC and other vehicles I have owned, I got poor mileage, hesitation, rough idle, and drank the fuel down like it was water.

Most people buy what's cheap, or is on sale. I am a person that believes in quality before quanity. I would rather pay 5-10cents more per gallon for fuel that runs better and gives me on average of 2-5 more miles per gallon.

What a lot of people don't know is, any engine that has a compresssion ratio of 9.1 or higher should be at minium 89 octane. Our Scion tC for ex. have a 9.6:1. compression which can burn 89 octane w/o an issue. The higher the octane the slower the burn. This means it burns more efficiently and cooler, giving better performance and mileage.

Not every vehicle on the road will respond to a higher octane. On average it takes 2-3 tanks of a higher grade of fuel to readjust the vehicles computer, Stoich (Air-Fuel Ratio). There also will be a difference on fuel mileage pending on where you live, whether or not you live above or below sea level. Less air coming into the engine and mixing with the fuel will affect the performance and gas mileage and vice versa. Its also going to depend on how you drive your vehicle as well.

Every or most gasoline company adds additives to their fuel, which help clean your engine, burn off deposits, gunk and allow your engine to perform more efficiently. I am not positive if there are more additives in 89 and 93 octane, but the smell is not as obnoxious as 87 octane. If your buying top-tier fuel like: Exxon/Mobil, Shell, or Chevron for ex. you'll find the fuel burns cleaner, offers better gas mileage and more performance. Now on the flipside of the coin, there is low quality fuels, which don't offer the best cleaning agents, lesser fuel milage, and poorer performance. I would sugest staying away from these as much as possible, or what we call Mom&Pop or No-Name gas stations. In most cases the fuel that they are selling is everyone's leftovers so you don't know what fuel your buying.

Everytime I fuel up, I keep a record of how many miles I went and how many gallons it took to fill my tank. By taking these figures, you can get your gas mileage. I also have a ScanGauge II that is mounted ontop of my steering column and gives me a read out of my: RPM's, MPH, air/fuel ratio, gas mileage, and other options as well. On the highway I'm getting 31-33 mpg at that is at 55mph.

There are two kinds of fuel we burn throughout the year. One is summer blend and the other is winter blend. The difference is, the winter blend has an additive in it that acts like an anti-freeze to keep the fuel from freezing and also allows for a faster warm up time. The winter blend doesn't give you the best fuel mileage, hence we use most fuel when the weather is below freezing and any vehicle uses most fuel at start up, verses idle. Most people believe that adding a bottle of Dry-Gas to the tank is necessary. Actually that is a myth, dry-gas is actually isopropyl alcohol. Most engines have rubber seals, dry-gas will dry those seals out, which over time can lead to other serious problems. Think of it as this: When we get acne we use a chemical to treat the acne, in some cases our faces dry out, that is the alcohol in the product. This applies the same to the seals in an engine. If you need to remove water or condensation from your tank, buy a bottle of fuel injection cleaner which has a water remover in it (Prestone, STP) and doesn't contain alcohol.

The other issue that is big right now is warranties. I know with higher end luxury cars/trucks/SUV's at most they require at minium 89 octane. Most people who buy these vehicles don't pay one bit of attention to the owners manual or the sticker that is inside most fuel doors. Those stickers are put there for a reason. When a vehicle is built, the computer and engine are tuned to burn a certain octane for maxium performance. In some cases running a fuel that is not required can void the vehicles warranty. This I know applies with most BMW's, Mercedes-Benz, Audi, Acura and Cadillac. The dealership will tell you that 87 octane is fine, but what they won't tell you is when the vehicle starts acting rough, or having problems they won't warranty using the wrong fuel. You'll end up paying out of pocket. The dealership is out to sell and make money...Period. So when something breaks or you need something fixed they want you to come back and open up your wallet and shell out the cash.

For anyone that believes that a higher octane is a waste of money or doesn't offer better performane, better gas mileage, smoother idle and less carbon build up, just try a few tanks and do your gas mileage. On average most people should see 2-5 more miles per gallon. If your running forced induction, then a higher octane would be required.

 

I have a auto tc and each time i step on it when it is already on the 4th gear,and I have unleaded gas on,it shifts to 2nd gear to give me the power I want. When I have premium gas, it only shifts down to 3rd and burns the gas quicker and gives me the power I want. If you can afford premium thendo it but if you can't then don't. For me its premium all the way because I know that its wayy cleaner than unleaded.

 

In the thread I posted, I forgot to include another important note. Most states are using Ethenol/E85 Fuel. For those that don't know much about it, its made from Corn. The reason for this new fuel is to help clean up the environment and the air. Also to help cut back on oil production. The down fall to Ethenol/E85 is that the fuel mileage is going to decrease as well and HP/Torque. I have heard a lot of consumers complaining about the new fuel and how poor it runs. It really makes no sense what so ever to produce a car/truck/SUV that is designed to get excellent fuel mileage, then turn around and make a gasoline that in return gives you less performance and fuel mileage. I can understand cleaning up our environment, but this method that EPA is pushing on consumers needs to be rethought. I feel bad for those guys/gals that have muscle cars and run a higher octane as it is, I can only imagine the problems their going to indure with this new fuel.

I have also heard that lawnmowers, chain saws, and other equipement are having issues with this garbage that is our gasoline. Its only going to be a matter of time before something changes, plus there is a rumor going around that a fuel additive may be made available to the market to add to the tank. I do know that with some vehicles on our roads today, some can not use E85/Ethenol. Vehicles that can take regular gas or E85 and its states that a fuel additive like Lucas, STP, Gumout, Sea Foam for ex. can not be added to fuel tank. Why this is, I haven't gotten enough information yet. I use fuel injection cleaners on a regular basis, every 2000-4000 miles and haven't had issues what so ever or ever had my engine get gummed up from using them.

Although I have seen the inside of many engines of other makes, models and years of different vehicles. The insides of a vehicle that ran on 87 octane all its life was very dirty and gummed up. Now the engines that ran 89 octane or higher consistently were much cleaner, and infact the valves, rings, seals and lifters and other parts had little or any build up.

 

You can put whatever you want in your car if you think it is helping - but instead of spending money on a higher grade, you'd still be better off buying a higher quality of gas (and no that doesn't mean just higher octane). I'm talking the top tier vendors... Shell, etc.

 

lol, so premium isn't unleaded, and the octane rating determines how clean it is?

 

this thread is full of FAIL

 

There actually a big misconception about what premium fuel is. To elaborate 89 octane is actually (Mid-Grade) or (Plus). 93 octane is (Premium) or (High Test). All gasoline being sold at the gas pumps is unleaded. Leaded gasoline is no longer being sold and hasn't been manufactured since the 70's or earlier if I am correct.

I recall reading up on an old article in the USA Today or NY Times saying that leaded gas was poisonus, but come to find out the tests that were being done were all wrong. The lead in gas wasn't the issue, it was having to due with Lead Paint and paint chips that children were eating. Hence why lead paint is no longer made, but some older homes still have it and why its so toxic. Leaded gas was actually better for engines, but since you can't buy leaded gas, a lead substitute/additive can be purchased from a local autoparts store, not recommend in fuel injected engines.

This whole thread would be great to hit the " MythBusters " with. I would love to see how this would all pan out, but since things in our world are so touch and go, time will tell.

 

My point was that it does not fill your engine with gunk..and yes I do get it at shell/mobil.I NEVER said that premium is not unleaded I said that it is cleaner than unleaded(87) so don't state things I never said.And go ahead,like how everyone in scionlife says"You pay for what you get"then keep on using that gas that is like water,and on the long run you'll see why

 

Not all Vtech's require a higher grade fuel, but I do know that with a Prelude (H22) they do require 89 octane or higher. Most of the Honda folks I have spoke with, they all say that a higher grade fuel should be used. Not all the Honda's were forced induction either.