What benifit(if any) mwould be gained from running hight octane gas in a stock WRX??????

better performance, no engine knock. It is worth the extra 10-20 cents per gallon.

What about using octane higher then the 91 or 92 Subaru suggests, like 94 or racing gas i see sold sometimes.

Have you guys seen the, I believe, Road & Track (or was it Automobile?) magazine this month? They have dyno result for different Octane gas.

I run Ultra 94 in mine almost all of the time. I haven't done any studies to see if it is giving me any more boost. When I used to have my 1990 Saab 900 Turbo, it would give me a little more boost when I ran 94 vs. 91. My brother's Talon gets a little more boost with the 94.

I also have a miata and have been told anything more than regular is just a waste of money, why does it give higher performance in the WRX is it because its turbo charged???

Turbo like more octane because you can run more boost before knock rears its head. Most modern turbo cars have knock sensors and they will let the turbo produce more boost if they don't see knock. They are mainly there to protect the engine if you run lower octane (86 or 87). They will retard the timing and reduce boost to prevent knock.

So will I see a differnece if I run 100 octane?????

My MY00 RS which is pretty much stock, and I use Sunoco 93 octane all the time. But I use it to help keep my engine clean. I saw a sign at a Mobil station that said ‘Premium keeps your engine clean’. The manual says that if quality gas is used it will eliminate the need for cleaning additives.

http://www.plauder-smilies.de/person/orangehat.gif Greg

I'm pretty sure there is a limit to the benefit. :) It would be nice though. :)

If you put a manual boost controller on the thing, you could crank the boost with 100 octane. Just make sure you have a EGT gauge to watch the exaust temps. :)

I think the ecu will advance timing if higher octane is used.

This topic has been brought up and difinitively answered so many times, it's ridiculous. Run a search on "octane rating." And you should be able to find answers to all the questions you could think to ask (as well as several you wouldn't even have imagined).

Jordan

I ran 107 for half a tank. The result was outstanding. I had instantaneous throttle response, and the car actually threw me back again like it used to before I got used to it. Higher octane means less detonation, thus more compression. You should always use the highest octane you can get.

Mike,

You're wrong. You should not always use the highest available octane fuel.

Higher octane does NOT give you higher performance directly. It does let you go higher by increasing the boost thus achieving higher performance.

I heard that some gas stations have some sort of gas detergent that makes the engine clean.. and they only put this in their premium(93) gas. Other than this, your car won't fly just because you put higher octane gas.

Higher octane gas just has higher tolerance of burning under higher pressure.

If you want to gain higher performance, try Jet fuel. :lol:

How about something other than a shouting match?

Now, every internal combustion engine has a set compression ratio. Usually around 9:1-11:1 in normally-aspirated cars and 8:1 in our turbo'ed WRX. You want to compress the air/fuel mixture in the combustion chamber and then lit it with the spark plug. What you don't want is pre-mature ignition, which is known as "knock", and is very bad for your engine.

Now, fuel has a octane number. The higher the number, the less it's likely to ignite on its own (and therefore knock). It will, however, not give you more power. Energy content should be the same in all gasoline grades.

For a regular sedan with a low compression (like 9:1), a 87-octane fuel is okay. Using higher octane fuel is just throwing money down the drain. However high compression engines or a turbocharged engines are designed to use high (usually 91) octane gas. If you use anything lower, knock sensors in the engine will retard timing, and avoid knock. However, you'll lose power. It should only be used in an emergency (when no 91+ octane fuel is available).

On the other hand, using a 94, 97 or 100 octane fuel in a stock WRX engine will NOT give you more power. Again, octane rating does NOT equal to more energy in the fuel. I've tried Sunoco 93 and 94 octane gas at Watkins Glen, running up to 115mph, always in 4-7k range, and observed NO difference in power between the two.

However, if you are using higher boost than stock, (or turboing a high compression EJ25) then you may encounter knocking with even 91 or 93 octane gas. In that case, a high octane fuel is warranted - not for power, but for the safety of your engine.

My conclusion? Use premium fuel (usually 91, 92 or 93) for your stock WRX. Don't go lower, and no need to go higher.

-Ray

Try reading the post: http://www.i-club.com/forums/showthread.php?s=&threadid=54015&highlight=Octane

Since it seems most can't or wont do a search before rattling off a question (or worse, an answer) I would like to repost the original text. Too bad its too long to fit here.

Essentially Ray, you are correct in your findings. :D

I really wish the octane question would die a quick, but horrible death. :D :D

rkkwan is correct

come on guys this question has been asked a million times

I was running 87 in my car untill Summer arrived. With the hot air, the engine was pinging pretty bad. 92 octane since then and no noticeable ping.

I meant better performance as in when you compare the premium grade to the regular grade with wrx. It is true that the ecu retards the timing to avoid knock, hence worsen the performance. If your car requires premium, use it. If not, don't waste your money.

Originally posted by tatical
The manual says that if quality gas is used it will eliminate the need for cleaning additives.

http://www.plauder-smilies.de/person/orangehat.gif Greg

I think it says that if you use the gas with the detergent in it you will never need additives. I use Chevron w/Techron

tatical-
I saw a sign at a Mobil station that said ‘Premium keeps your engine clean’. The manual says that if quality gas is used it will eliminate the need for cleaning additives.
Where did you get that high quality is high octane? Not the same. And where did you get that someone trying to sell you something would not lie to you. Hey, I've got some magic gas I'll sell you for $3.00 a gallon. It'll make your car fly, literally. If you want, I can make a sign for it.

Check consumer reports extensive tests on different brands of gas. They've found differences in a few. BUT, it is only in a few crap brands, not octanes.

If you want to know the correlation between octane, compression, boost, knock, and why cats always land on their feet, check here:http://www.howstuffworks.com/search.php?terms=octane

Can we make this site required reading before posting?

OR, like everyone else has said, do a search on this site.

Mike DTD WRX said:
I ran 107 for half a tank. The result was outstanding. I had instantaneous throttle response, and the car actually threw me back again like it used to before I got used to it. Higher octane means less detonation, thus more compression. You should always use the highest octane you can get.
No, you didn't, and no you shouldn't. This post is a wealth of misinformation. You have no info to support this, aside from a butt dyno. Under your scenario, I'd go get a half tank of 93, fill the other half with octane boost, and get somewhere around 1000 HP, throttle response by telepathy, and 6 second 1/4 miles. According to my arse, of course. I only hope your response was meant to be funny. Terrible misinformation if not.

illmatic said:
I think the ecu will advance timing if higher octane is used.
You might be right. The last 15 times this was discussed it was determined that this is possible, but may or may not happen. Furthermore, if it did, you probably wouldn't see much of anything at all. How about someone finally puts a fork in this by going to a dyno, doing a base run with 91, and then resetting the ECU, and running on 107, or whatever ridiculous octane you can mix up. I bet you'd see a 1 HP gain, at best. And it might not be but in one spot in the powerband. All, of couse, speculation.

Can someone get on a dyno and finally bury this one?

Check this out.

http://www.caranddriver.com/xp/Caranddriver/features/2001/november/200111_feature_gasoline.xml?&ID=Beyond/xp/Caranddriver/features/2001/november/20011&page=1

Originally posted by RoadRashed
Check this out.

http://www.caranddriver.com/xp/Caranddriver/features/2001/november/200111_feature_gasoline.xml?&ID=Beyond/xp/Caranddriver/features/2001/november/20011&page=1

I had gotten similar results to the Honda Accord (power loss, worse 1/4 mile times) when I tested this on my OBS a long while back.

Energy content should be the same in all gasoline grades.

The key here is should be the same. For a variety of reasons, this is not always the case. This could quite likely explain the reason why the Accord actually lost power.

As said before, using higher octane than required will not give you more power.

I'll sum up what that article said, for those of you who can't read.

Tested three cars on higher and lower octane. Basically, they determined a minor change, both up and down, on three different cars. They drew no conclusion, aside from it could be within a margin of error, and have nothing to do with the gas. Then they summed it up with:

"Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends, as any performance gain realized will surely be far less than the percentage hike in price. Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by about the same percent they save at the pump. If the car is sufficiently new and sophisticated, it may not suffer any ill effects, but all such skinflints should be ready to switch back to premium at the first sign of knock or other drivability woes. And finally, if a car calibrated for regular fuel begins to knock on anything less than premium or midgrade, owners should invest in a tuneup, emissions-control-system repair, or detergent additives to solve, rather than bandage, the root problem. Class dismissed. "

Now, can we make a FAQ out of this, and dismiss it?

Energy content should be the same in all gasoline grades.

Actually, higher octane means less energy content by a small margin, but the higher compression allowed by the higher octane allows more power to be used from it.

I think the location of your gas station is more important. Some stations take ages to run down their stocks, others sell it quickly. The quality of gas can vary enourmously from station to station. I read about a french rally team that were nearly banned for using special fuel. They got the scrutineers to get some fuel from the same station they did, and it was 102 RON!!!
There's a couple of threads on scoobynet.co.uk about optimax fuel which is supposed to be higher than average octane, go look at those.

You guys are right, use the search. No need to ever post a question that has been answered here before. The last thing this site needs is people discussing topics that have been discussed in the past. We're sorry if these questions offend some of you. My advice don't read those threads and don't reply to them. But some of us peons around here like to reads these threads and get new insights from other members. I don't care how many times it's been ask before. If someone doesn't have the answered they're looking for, they have a right to post their question.

I own a bone STOCK WRX wagon, and decided for Shiites&Giggles to fill the tank w/100 octane racing gas. Two things to note:
1-Cost me 40bucks
2-Felt NO difference in performance, none. And the wx was cooperating during this time period (ie low humidity, cooler temps).

I did a variety of driving and by seat-of-the-pants impressions, nothing was diff't in terms of acceleration, pull, whatever you want to call it. Keep in mind though, that this was on a completely stock WRX... 93 Octane is fine w/me, FWIW...

Streetman-
It seems like you’ve misunderstood my post...
Where did you get that high quality is high octane? Not the same.

I’m guessing that you don’t know that some fuel companies put extra additives (namely cleaning additives) into their higher octane gas. Higher octane + Extra additives = Higher quality. Please keep in mind that higher quality doesn't always equal better performance.

And where did you get that someone trying to sell you something would not lie to you. Hey, I've got some magic gas I'll sell you for $3.00 a gallon. It'll make your car fly, literally. If you want, I can make a sign for it.

You’re jumping to conclusions. I didn’t say I thought anyone was dishonest or truthful. The people with WRXs or any other car that requires 91 or higher must rely on signs. They go to the pump and look for the button with their desired octane number, push it, and pump it. You can’t believe every sign you see, but I see nothing wrong with believing a reasonable claim.

http://www.plauder-smilies.de/person/fro.gif Greg

Has anybody tried filling with half tank of 87 regular and half tank of 91 supereme gas, just to save some money?:)