100 Octane?
 

I mixed two gallons of 100 Octane with my usual 91 V Power, the butt dyno feels the difference. Just wondering if anyone else has had experience with higher octane fuel? Is it safe? What if the whole tank is 100 octane? lol

Just found this and pumped some by the 76 in Saratoga just before heading up 9 to Alice's.

https://sphotos-a.xx.fbcdn.net/hphot...66604075_n.jpg

Unless your car is tuned for it, you will start to lose performance if the octane rating gets too high. Bringing 91 CA gas up to 94-95 can be a good thing, but straight 100 will probably be a waste of money. If you normally put in 10gal, try 3 gal 100 w/ 7gal 91. That should put you in the high 93 range, and the car will love it. Most I would go is 4gal:6gal using 100:91 without a tune.

yeah a bunch of us did the 94 octane or 91 + 100 octane mix this weekend, and we were all talking after about how we could feel the difference. What a shame we have to live with 91 all the time here or pay through the nose to get the hi octane stuff. Everyone else in the country gets that extra bit of power on a regular basis. :(

Extra octane in your fuel does NOTHING unless you're tuned for it. Octane is just how fast, and hot the fuel burns.

Running 100 octane without a tune is more likely to cause damage than gain performance.

PLUS if you really knew what you were doing you'd just be tuned for E85 (which is about 104 octane) because it's a million times cheaper than race fuel and slightly easier to find.

Even the autoX 86 cars running E85 or 100 octane WITH A TUNE for it are only seeing it give them 3-6 WHP, this is not something you could likely feel with a "butt dyno" especially since none of you are tuned for it.

I've been mixing for the past few weeks, and can definitely tell the difference. Which actually surprised me, cause I didn't think I would (I didn't think our engines have enough compression to make a difference). First time I tried it was right before the last Mt Ham drive, and now I'm doing it for even for around town 'normal driving'.

There's a couple of places with 100octane I know and there's another near almaden expressway. The problem is that there's so few and far between stations with racing fuel let alone flexfuel (e85). If there's a way we can consistently obtain flexfuel i'd probably be doing the tune right now for it.

PMok is right. I hadn't said anything to them yet, but I certainly felt, and am still noticing the difference (not quite done with that tank yet). When you drive a particular route regularly at 91, then you bring the car to its desired 94, you definitely notice it. It's not so much "extra" power, but a better responsiveness.

Gotta agree with Blaine too. If you start going higher, you're not really going to notice anything more. The only reason we noticed the increase to 94 is because the car is tuned for that.

From the owner's manual: "The engine is designed to operate at maximum performance using unleaded gasoline with an octane rating of 93 or higher. If 93 fuel is not readily available in your area, unleaded gasoline with an octane rating of 91 may be used with no detriment to engine durability or driveability. However, you may notice a slight decrease in maximum engine performance and you may hear some knocking (pinking) of an engine while using 91 fuel."

Interesting wording, and hints that the stock tune may have some wiggle room when it comes to octane. I've definitely noticed improvement with filling up with full tanks of 94 or 100, or when mixing 91 and 100. It's not crazy dramatic, but it really smooths out the powerband, and the engine feels especially rev happy above 4k.

I hadn't heard that running 100 could damage anything. I would think that they would make a note of that in the manual versus saying "93 or higher". Also, they ran 100 octane in the cars at the Scion celebrity racing event:

"The cars run on 100-octane race fuel -- there's no performance gain, but it levels out the knock sensors for even running."

http://www.autoweek.com/article/2013...NEWS/130319965

The celeb race cars where tuned.

Trust me guys, the butt dyno is not scientific and you guys are pretty much just pissing in the wind here.

Even with a few extra ponies a V6 Caravan or Odyssey will still smoke you on the highway. If you bought this car for power and straight line speed you have the wrong car.

I'm not sure anyone that's posted about their experiences in this thread has claimed a measurable horsepower increase. It's more about how the engine responds and behaves, not like "oh it gives me +10 hp".

Also, I'm not seeing where it talks about the celebrity race cars being tuned. Link?

This is exactly what I thought after filling up at Sunol, no extra power, just better response. My guess would be that at 91, the ecu just pulls the timing just slightly to compensate.

Also, food for thought, our ecu's have a learning span to safely adjust itself on the local fuel. So a tank of 93+ won't really give you any immediate gains (if any) since it has been calibrated to run on all those tanks of 91 we'll already been running. Some people post gains after a tune, but that could possibly be the ecu just being reset and not getting the chance to "re-learn" yet.

100 octane fuel will LOSE HP in a stock car....... When tuned for it, there will be a gain from increasing timing due to reduced knocks.... Yes our crappy CA gas is only 91....but with a modern fuel injection system like our cars have its fine....

How does it lose hp?

I don't know about hp but my mpg seems a little bit better with my heavy foot on 94 octane than 91.

Octane rating is really a measure of how resistant to combustion the fuel is. I guess the theory of it losing power on 100 octane is that the fuel is more resistant to burning, so not all of the fuel burns and you don't get the full power out of the charge. Meanwhile on 91, your getting the same amount of fuel and roughly the same energy content except ALL of it is burning creating power.

The advantage of higher octane is you can run a higher compression ratio without knocking (detonation, which damages your engine) which is thermodynamically more efficient resulting in a power gain. If your engine isn't tuned to run higher octane you're just throwing money away and in some cases, you may be losing power.

I don't know if my first paragraph holds true for our cars, that's something that will have to be tested, but the idea is sound. If your car isn't tuned for higher octane, it won't do much other than lighten your wallet.

If the extra $8 a tank is worth the psychological benefits who am I to stop you? If you're actually trying to gain measurable speed for competition that's what practice sessions are for, although you'd probably get more time out of tire pressure adjustments or playing with your driving technique.

Has anyone mixed E85? I've been putting a bit of 100 octane in each tank to boost to 93 or 94, and was wondering if it would be cheaper to use E85. I have heard that if your car isn't set up for E85, it will cause problems.

Why are you wasting money on mixing in some 100 octane in the first place?

Your car might gain 1/8th of a WHP, but maybe not even that. Extra octane doesn't help you unless your engine is tuned and maximized for it. It certainly isn't "better" for you car. Buying quality fuel without additives (like extra ethanol) is more important than octane. I'd put 87 from Shell/Chevron in my car before 93 from Joe's Fuel Shack.

Octane rating is just the temperature at which the fuel detonates (better explanation a few posts up). It's not a "better" fuel.

Yes, I understand that (see my earlier post). Maybe it's a 'placebo effect', but it seems to me that the engine tends to hesitate slightly with 91 octane when I jump on it, and not so much with the higher mix. Maybe I'm getting crappy gas from Arco(BP), Valero, etc and the 76 100 Octane is better gas. It was your earlier post that actually got me thinking about using the E85. I'm a cheap skate, so I never use a higher octane like some folks that think it's better gas. I put regular in my wife's MDX that calls for premium, haven't heard a knock yet.

Check my post earlier in the thread, I agree, car ecu is programmed to run 93, but "learns" and compensates to run CA 91 gas by sacrificing some response (not necessarily power).

I believe you will need a tune (Ecutek, etc) to run E85 properly without messing up your engine. Had a few guys out here who have tried E85, but I guess it could be tricky finding a gas station (not as common here in the bay compared to the valley)

If you're cheap why do you spend more on pointless fuel for your car? The difference between 91 and 93 is vertically immeasurable from a performance standpoint while driving the car. Literally on a stock tuned car the dyno would read the exact same. Maybe 10ths of a HP.

Poor fuel would cause hesitation, the ECU is smart enough to know its being fed 91 and shouldn't hesitate vs. 93.

The reason you don't hear knocks in the MDX is the ECU can adjusting the timing for 87. BRZ/FR-S will do the same. Other than loosing a HP or so you can safely run 87 in your BRZ.

I know I'm necrobumping this a bit but here goes.

I subjectively feel performance and smoothness gains from 91 up to about 95 octane, above that I think it falls off on a stock tune. I understand that higher octane gas doesn't "add power" but giving the ecu the ability to run more aggressive timings does add power even on a stock tune.

I'm curious to see if anyone has any dyno results from playing with octanes on a stock tune. I think there is more gains here than people realize. I would expect at least 5-7hp gain. Timing on high compression and turbo engines can make quite a difference.

The ecu learning does make timing changes significant enough to pop CEL's if you change fuels. I was running a mix of 100/91 for about 94 octane, my wife put in some 91 and I got a CEL on my first highway pull.

Anyone have any real numbers on this?

A local guy Rick had custom dyno tuning for 91 oct and then 94 oct. His car was not stock however, it had exhaust installed.
He gained 1whp and 1tq between 91 to 94.

http://86drive.com/2014/03/01/na-brz...n-engineering/

I dont know if mental feeling or what.
I tried both, I felt that the E85 has more power than the 100 octane.