87 vs 91 octane
 

Any time there's an increase in gas prices you'll often see news stories posing the question: "Is premium fuel worth the premium price?" After the "expert" gives his two cents, the reporter will often conclude thus: "There you have it-if your vehicle runs fine on regular, stop throwing your money away on premium!" The average consumer can easily be lulled to the conclusion that there are no benefits whatsoever from running gasoline that costs a premium price of 20 cents more per gallon. The logic experts use to justify their claims is straightforward: If you run 87 octane and your car doesn't knock or ping, you'll see no difference if you use 89 or 91 octane. There are also claims that if your vehicle is only designed to run on 87 octane, you could possibly encounter problems from using higher octane.
To test the "premium gasoline is a waste of money" theory, we borrowed an unmodified Jetta 2.5L designed to run on 87 octane. In order to get a more accurate read on performance and pick up on any drivability differences, we decided to do more than just dyno tests. We performed the various tests using four tanks of gasoline. Under real-world driving conditions, the tank was run from full to empty first on 87, then on 91, and then back to 87. With the last remnants of 87 the car was dynoed until completely empty, then refilled with 91 and dynoed again.

Vehicle Data
Engine: 2.5-liter I5, dohc, 20-valve
Transmission: Six-speed automatic
Mileage: 4,520
Current modifications: None Dyno Type:
Six-speed automatic
Baseline : 87 octane
Performance
Temperature: 66° F
Humidity:15% Peak Power: 133 hp @ 5976 rpm
Peak Torque: 134 lb-ft @ 3444 rpm

Test Notes
All testing was performed on the same day. All horsepower and torque numbers are quoted at the wheels. Keep in mind that the properly calibrated "Mustang" dyno produces more accurate real world numbers. While these numbers might seem low when compared to figures gathered from a Dynojet, what is important is the differences between each dyno run. When we strapped the Jetta to the dyno the needle of the fuel gauge was right at the red marks and we dynode until the fuel light appeared. All five of the Jetta's 87 octane runs were virtually identical with no major variations and at no time did the vehicle experience any knocking or pinging.

Test 1
Performance
Peak power: 138 hp @ 5908 rpm
Peak torque: 146 lb-ft @ 4060 rpm
Peak power gain: 7 hp @ 5790 rpm
Peak torque gain: 13 lb-ft @ 4150 rpm
Temperature: 67° F
Humidity: 13%
Pros
• Increase of 1-2 mpg
• Increased throttle response and smoother power transitions
• Reduce risk of knocking or pinging
• Reduce risk of horsepower loss from heat soak

Cons
• $0.20 per gallon price premium

Test Notes
We took the Jetta to a gas station about a mile away from the dyno facility and filled it up with 13.74 gallons of 91 octane gasoline. We then drove the vehicle for 25 miles to give the vehicle a chance to adapt to the octane increase and make sure there was no 87 octane left in the lines.

Conclusion
Does higher octane fuel makeadifference on all vehicles? It did in this case. Because of VW's advanced electronics and highly adaptive engine management, the Jetta 2.5L has an elastic response to a changes in octane levels. Once we put in the 87 octane, we could feel the drop in performance-less responsive, less peppy, and overall just different. The engine instantly detected the reduced octane levels and adapted for standard performance. This analysis was based on more than 1,200 miles of driving over a week.
Switching between the two octanes allowed us to use the dyno to detect and confirm or refute any driving subtleties we noticed during the week. Even though the Jetta's gas tank flap advises 87 octane, the dyno graphs clearly show that running premium gasoline does have performance benefits including, a slight increase in fueleconomy. In the end, you get what you pay for. If you want standard performance use standard gasoline. But if you want premium performance, pay for premium gas.

COSTS SUMMARY
91 OCTANE FUEL: .20/GALLON AVERAGE PREMIUM $.20

thumbs up! I think the 91 octane is definetly worth the premium, but that could just be me

I'm sure someone will disagree with this statement, but I put in 91 on my TC and I think it makes a lot of difference, feels better, feel as if it has more power, and the engine idles a bit softer...

Funny thing is that the above, per experience is true based on my 2 Nissan Sentras SE-R. I have a regular auto SE-R and a SE-R Spec V.

Both use premium gas per the recomendations in the owners manual, and trust me, if you put anything less than that, the car feel as if its going to die and blow up; it shakes, it sounds awful, it has no power. To agree further more, the SE-R 2.5 motor is the same as the altima, but you can put 87 in an altima but not in the SE-R, as stated above the computer system plays a big part to adapt to decrease/increase performace in relation to the garbage we throw in the gas tank...I'm no expert but from experience, I agree with the above statement. I'll rather pay 20 cents more a gallon and feel confortable and to get 87 and have my cars feel like crap.

Thanks for the write up!

Just go by what the manual says. :ponder:

i feel the same way,,even though people tell me using premium on my scion is a waste,i still use it,cause car feels more alive i dont have to clean the injectors as often,overall feels alot more responsive,unlike 87 where it wasnr as good

Edit: nvm. Click on the graph to see results.

This data is irrelevant to the tC. You can't extrapolate results from one car and apply them to all cars, including the tC.

Also 87 octane is no more or less "dirty" than 91/93 octane. Saying you "don't have to clean the injectors as often" is complete nonsense.

Lastly, if you look at the power curves, you can see that for the VW 2.5L, all the gains were at the high-end of the rev-range, and actually included a loss of low-end torque. I don't know about you guys, but I'm not constantly flogging my engine, and even if the tC could gain power overall (which has yet to be proven), if the result of premium fuel were in any way similar to that of the VW there would be no gains when putting around town. The horsepower curves didn't diverge until ~3650 RPM and torque wasn't consistently greater until 3500 RPM in the picture above.

as they say....use premium to achieve the maximum performance of the vehicle,rather its true or not..i know for a fact i dont have to clean my injectors as often as i did with regular maybe mine are shot..overall by me premium is 50 cents more..why not use it..the car reacts to it alot better then regular..but yea all cars are different....i just responded to the other person that mention using premium in his scion

Octane should make little difference to everyday driving, but if you want a bit more, I am a believer that higher octane helps. Combustion temps are different, for better or worse, which may explain why ppl feel that a change in octane helps. Again, depending on how you drive, periodic induction/injector cleaning is necessary, to alleviate carbon buildup. True the same detergents are in all grades, but exhaust temp is used for minute timing adjustments, and octane affects that. This is the power that some claim to feel, while others say nothing's changed.

You haven't read the manual, have you?

I have.

I could be mistaken, but I believe the manual said to use at least 87 octane. It did not say to ONLY use 87 octane.

I think 91 octane could be better at times, but I've never seen a noticeable difference. The gas mileage did not seem to increase a noticeable amount. However, the price after filling the tank was noticeable.

To conclude: It is not worth it to me to fill up with premium. Just don't get the cheap Arco stuff. Use Shell or Chevron/76.

I didn't say anything about using only 87 and I didn't condemn using other than 87. IIRC, the manual says something like 87 recommended, research 91. Besides, I have an xB2, our manuals probably differ. I posted what I posted just to state that instead of speculating all of these "performance benefits" to using higher octane, to just go by what the manual says.

I understood that you were suggesting to use 87. I also agree that 87 is more logical. You are correct, the 2011 tC owners manual also says "87 recommended, research 91" (at least it sounds very familiar, I don't feel like going out to the car and digging up the manual)

But that manual does not say to ONLY use 87, so I doubt there will be any problems with using higher octane. The only difference might be 1-2 more MPG or so, and a few horse power, which would only be noticeable on the Dyno, and your wallet. Pick which one is more important.

For daily driving - 87 octane
For the track - 91 or higher; if it really works.

I doubt the possibility of increased gas mileage is worth the extra .10-.20 cents more per gallon.

But it's your car, and the options are there, so pick what you want.

Octane ratings are always specified as a minimum because all that octane means is resistance to detonation. Any car that takes 87 can run on 91/93. It is not indicative of any potential gains (or lack thereof) from a higher octane.

Cool story bro, now do this for the tc2.

I have a TC2 now but before all I had were Hondas wich have high compression
Hondas DOHC VTEC engines are all over 10 compression or even higher
and says 91 only or higher okey whats point the rule of thumb always has been if your compression is 10 and higher like the TC2 which uses the AR engine which is 10.4:1 use 91 now the car has 14.5 gallon fuel tank I live la so 91 about $4.50 and 87 about $4.30 87 is $62.35 and 91 is $65.25 to fill up the tank difference $2.9 you could come come up with excuses but cant afford $3 extra a tank a energy drinks cost the same old TC1 guys could argue this because of their compression 2az-fe 9.6:1 its up to you here some facts
The compression ratio of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity. It is a fundamental specification for many common combustion engines.
In a piston engine it is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke.[1]
Picture a cylinder and its combustion chamber with the piston at the bottom of its stroke containing 1000 cc of air (900 cc in the cylinder plus 100 cc in the combustion chamber). When the piston has moved up to the top of its stroke inside the cylinder, and the remaining volume inside the head or combustion chamber has been reduced to 100 cc, then the compression ratio would be proportionally described as 1000:100, or with fractional reduction, a 10:1 compression ratio.
A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency.[citation needed] High ratios place the available oxygen and fuel molecules into a reduced space along with the adiabatic heat of compression–causing better mixing and evaporation of the fuel droplets.[citation needed] Thus they allow increased power at the moment of ignition and the extraction of more useful work from that power by expanding the hot gas to a greater degree.[citation needed]
Higher compression ratios will however make gasoline engines subject to engine knocking if lower octane-rated fuel is used, also known as detonation. This can reduce efficiency or damage the engine if knock sensors are not present to retard the timing. However, knock sensors have been a requirement of the OBD-II specification used in 1996 model year vehicles and newer.

In other words use higher octane to reduce Knock and better A/F Ratios unless you want to be Cheap Cheap Cheap

The tC doesn't knock on 87. :rolleyes:

Octane has nothing to do with A/F ratios, either. Cars that can utilize higher-octane fuel (such as flex-fuel vehicles) will advance the ignition timing.

I never said the engine knocks the owners manual says you can use 87 but it also states research was done on 91 now why they conduct their tests higher octane I tell you why go to the first thread Reduce risk of knocking or pinging key word reduce not eliminate

Detonation can be prevented by any or all of the following techniques: the use of a fuel with high octane rating, which increases the combustion temperature of the fuel and reduces the proclivity to detonate; enriching the fuel/air ratio, which adds extra fuel to the mixture and increases the cooling effect when the fuel vaporizes in the cylinder; reducing peak cylinder pressure by increasing the engine revolutions

There's no risk of detonation running 87.

heres the deal...ive seen lots of threads aguring over regular vs premium,i say put in what you want,its your car and your $$$$$...end of story,rather you feel a difference or not....you know your car and what you experience...

^^^ Agreed

No.
The owners manual is referring to what is known as "Research Octane Number" or RON. It is a different method of measuring the octane of fuel. There is also a "Motor Octane Number" or MON. At the pumps in the US and Canada, octanes are measured in AKI (Anti-Knock Index). Some countries use RON to rate gasoline so the manual states the equivalent rating.

87 AKI = 91 RON

http://en.wikipedia.org/wiki/Octane_rating

I'm sure you're being sincere, but your post is a rather classic answer non-answer. Also, you can't rely on people to really don't know their own vehicles. Human perceptions are terrifyingly fallible, e.g., we can convince ourselves of a great many things that aren't true; conversely, we can be blissfully unaware of things that are true and staring us in the face.

Objective data (i.e., scientifically valid testing) would be much more helpful. I wish I could do that for us but I lack both the equipment and experience.

I have been eye balling this post but dident want to comment untill I tryed it out for myself. Best Average gas milage I ever got with a tank of 87=26.4 with 91= 27.1. I used 2 tanks of each, alternating to get a good feel before I posted. I do about 38 miles per day on the highway, and about 11 miles on city streets per day. My car is a manual, and does not know what 4K rpm's feels like yet (waiting till after I change the oil) and the only engine mod I have is a drop in K&N. More important to me than gas milage is the diffrence in throttle response. On 87, at about 2100-2900, it feels very sluggish, especially in 2nd gear. I have to wait for it to get to 3k to get any sort of power. On 91, I dont ever feel this. I have power to spare at any rpm. It could just be me, but thats how I feel about it. Do I like paying 30 cents more per gallon? Absolutly not, but like someone eles had pointed out, its less than a $5 diffrence per fill up. One less can of skoal, and I have payed for my premium gas for the week! Now all I have to do if figure out how to cut back on my nicotine addiction...........

Please....use....periods and punctuation.... X.X

I've been using 93 and now using 91 feels sluggish :(

Did you know that a well maintained vehicle can improve fuel efficiency by up to 40 per cent? Test your fuel knowledge to discover some useful tips to prolong the life of your engine and save a few dollars at the pump.
True or false?
1. All gasolines are the same.
2. Regular engine maintenance can help save you money on fuel.
3. Octane levels in fuel don't make a difference.
4. Tire pressure can affect the fuel-efficiency of your vehicle.
5. The faster you drive, the faster you burn fuel.
Answers:
1. False. "Gasoline choice plays a vital role in the cleanliness and performance of an engine," confirms Ken Mitchell, an engineer from Shell Canada.
"If you've been using a lower-quality gasoline, there may be build-up of "engine gunk," which can negatively affect engine performance. Protecting your engine from gunk is as simple as using a high-quality gasoline, like all three grades of Shell Nitrogen Enriched Gasoline."
2. True. Regular servicing and following the service recommendations for your vehicle, such as changing the air filter, spark plugs, engine oil and other fluids ensure optimum performance and fuel efficiency.
A poorly maintained vehicle can boost fuel consumption by up to 15 per cent and increases emissions by even more.
3. False. When a lower octane fuel is used in an engine designed for higher octane, engine knocking may occur, causing the car to shudder and lose performance.
Using the right octane for your engine ensures maximum fuel economy and fewer emissions.
4. True. Operating a vehicle with just one tire under-inflated by eight psi (56 kPa) can increase vehicle fuel consumption by four per cent.
5. True. The faster you drive, the more wind resistance you'll encounter and the more fuel your vehicle will consume to maintain speed.
Reducing your speed to 90 km/h from 110 km/h saves up to 20 per cent of your fuel.
www.newscanada.com

2010 Volkswagen GTI: The Effect Of Octane On Its Power

By Jason Kavanagh | April 26, 2011




http://blogs.insideline.com/roadtest...x477-85661.jpg
A few weeks back, one of our editors filled our longterm 2010 Volkswagen GTI's tank with 87 octane. Whether VW intended for this to happen or not, reality has a way of rendering such things moot.
Then we had a bright -- if obvious -- idea: let's do a dyno test to quantify just how much power this little hatch loses as a result of the lower octane.
It went down like this: We ran that tank of 87-ish octane down to nearly empty and refilled with 87 to ensure that the only thing in the tank was 87 octane. That, and it would give the electronic German brain on board adequate opportunity to recalibrate itself for the lower octane.
Then we dynoed it, performing as many runs as necessary to achieve a stable and consistent result.
Afterwards, we ran that tank down and refilled with 91 octane (that's the highest we get for premium fuel here in California), ran that tank down and refilled again with 91. Same logic as before.
We hit the dyno rollers again a few days later. Here's the result:

http://blogs.insideline.com/roadtest...x477-85667.jpg
Peak Power (hp) Peak Torque (lb-ft)
91 octane 207 219
87 octane 203 216
Peak numbers don't tell the whole story, as the largest observed differences at any given engine speed were 10 hp and 11 lb-ft.
In summary, 87 octane hasn't had a tremendous effect on our GTI's ability to hustle. Surprised? I was. I expected a larger difference than this.
It's likely that although the output is similar, exhaust gas temperatures may not be, as less ignition timing can be run with 87 octane. As a result, there might be:

• more enrichment on 87 octane, degrading full- or near-full-load fuel economy
• less altitude margin with 87 octane, and a greater power difference might be observed at high elevation. Sorry, I don't plan on repeating this test in Denver.

Note that modern engine controllers are quite adept at monitoring knock activity and adjusting accordingly. I heard not a single ping when running the snot out of this car on the dyno in either test. If you put 87 octane in your twenty year-old turbo car and gave it the wood, you might make engine soup.
Speaking of dynos, we dyno-tested our GTI on 91 octane last year, so why re-test it? I wanted to ensure similar weather conditions between the two octane dyno tests to eliminate that as a variable to the extent that I could. There are certain things that are still beyond my control, and weather is one of them. Across these two dyno test days, the temperature was within 9 degrees and ambient pressure was within 0.04 in Hg. That's about as close as anyone could ask for.
Weather has a different effect on modern turbocharged cars than it does on supercharged or normally aspirated cars. Here's why: power depends largely on the airflow rate into the engine. Turbo cars have the unique ability to regulate that airflow independently of ambient air density -- unlike non-turbo engines, turbo'd ones can actively manipulate boost pressure so that the same amount of flow enters the engine over a very broad range of ambient conditions. There are limits to this, of course, but the upshot is that turbo engines don't suffer nearly the power loss of a non-turbo engine when, say, climbing a long grade.
Temperature, however, does affect how much timing a turbo engine can run (due to knock), so in that respect weather has an indirect affect on the output of a turbo engine. The thing is, weather correction factors only account for density changes, which is why SAE does not apply weather correction to turbocharged cars, and neither do we.

http://www.gixxer.com/forums/showthr...t=226570:eyes:
This guy put nos energy drink in his tank :crazy:

Since no one has done a true test on a 2011 scion TC for 91 vs 87 or even 93 octane ratings I can go only conclude from other car tests car engine specs as a comparison
2010 Jetta 2.5l

• Engine: 2.5L in-line 5 double overhead cam ( 9.5 :1 compression ratio ; four valves per cylinder)
• Fuel: unleaded ( 87 octane)
• Fuel consumption: city= 23 (mpg); highway= 30 (mpg); combined= 25 (mpg); vehicle range: 364 miles
• Multi-point injection fuel system
• 14.5 gallon fuel tank
• Power: 170 HP ( 127 kW) @ 5,700 rpm; 177 ft lb of torque ( 240 Nm) @ 4,250 rpm

2011 Scion TC

• Engine: 2.5L in-linefour-cylinder DOHC with variable valve timing and four valves per cylinder
• Unleaded fuel
• Fuel economy: EPA (08):, 23MPG city, 31 MPG highway, 26 MPG combined and 378 mi. range
• Multi-point fuel injection
• 14.5gallon fuel tank
• Power (SAE): 180 hp @ 6,000 rpm; 173 ft lb of torque @ 4,100 rpm

2010 GTi

• Turbo compressor
• Engine: 2.0L in-line 4 double overhead cam with VVT ( 9.6 :1 compression ratio ; four valves per cylinder)
• Fuel: premium unleaded ( 91 octane)
• Fuel consumption: city= 21 (mpg); highway= 31 (mpg); combined= 25 (mpg); vehicle range: 364 miles
• Gasoline direct injection fuel system
• 14.5 gallon fuel tank
• Power: 200 HP ( 149 kW) @ 5,100 rpm; 207 ft lb of torque ( 281 Nm) @ 1,800 rpm

relax it is just a forum,,,,,.......!!!!!!!!!!!!:eyes:

on this forum we have had many a discussion on this subject with poor results.

http://www.yarisworld.com/forums/sho...ghlight=OCTANE

N/A vs Turbo. Unless your tC has forced induction, then it's pretty much useless. See

British petrol's minimum rating is 95 Octane by American standard, which is the highest-available, here. In essence, whenever you buy British regular, you're buying American Premium. The higher octane rating at minimum, is around the performance area for most mid-range cars. Adding even more Octane will have less notable effect than using American low-octane as the control against British high-octane.

This test is not for the American market

Ok well, she's talking to a sales person selling fuel, and he mentions force induction. The only real test if someone was to do with with our tCs. The rest is all speculation.

You sure it doesn't just reference the minimum octane as published on the pump and the minimum research octane number? (published octane being RON+MON/2, and MON being about 8-10 less than RON. When I was in Europe, they always used RON, and given how popular they are with military members, it's good to know what the RON requirement is.

I put 87 in my 07 tC 4yrs, might try 89oct little step up, but not gonna put 91 in it for sure. two pages, no one saying anything about 89oct?

2 octane probably won't be much of a difference.

I think we should make a poll fo rthe three octane who use the most.