i run regular in my s4 t2. it is stock, thats all it needs.

if you are putting preminum in your stock T2, you are wasting your money.

and... your car feels faster due to the placebo effect.

 

Wheres that big thread from along time ago that everyone argued in for like 5 month's. High octain for modified turbo's 87 for N/A engines.

IM AN 87 OCTAINER!!

 

The S4 TII owners manual calls for 87.

 

why risk it here its only 20 cents more for premium and normally premium has more dtergents added to it like amaco ultimate for ex.

 

octane has nothing to do with how rich/lean the car is running. that is a matter of tuning the fuel pressure, pulse width on the injectors and what size injectors your using.

octane has again nothing to do with rich lean

 

myth

 

Wow this suprises me. Its pretty obvious, that no matter what engine, be it Piston or Rotary, that Boosted cars require a certain octane gas. You see boys and girls, when the air/fuel mixture gets sucked in, it gets compressed and ignites. On a boosted car, the air is compressed together and that causes it to heat up. Certain gas, lets say with an 87 octane rating, can't withstand that added heat and pressure and it actually ignites before the combustion stroke.

That ladies, is called detonation. 87 Octane gas for example, means that the gas is composed of 87 Octane and 13 Heptane. Heptane is that bad little element that makes it explode earlier and be more susceptable to detonating before its supposed to. Now, Premium gas has a higher grade of octane, lets say 91. that means that it has 91 octane and 9 Heptane, thus being much more resistant to ignition before its supposed to be.

if your using a boosted car, go with 90 at least, you'l be sorry if you don't. Might not be today or tomorrow, but it'l happen.

 

I run 93 in all my cars regardless.

People say you are wasting your money, I say I am not. I know for a fact in my '78. when I ran regular my plugs fouled easier and were carboned up like crazy and so weas the engine internals. when I ran 93 with new plugs I haven't had to change them in 6 years. Here is why. I pulled them out and they were only a little bit eaten away but still were clean but discoloured with no black carbon build up. I fouled the same kind of plugs with 87 gas in less than 2 years on the same driving habits.

I know the difference it makes in my cars. You can say what you want but I know better. Strangely enough I have had very little issues with my cars since I run the highest grade oils, fuels, coolant, and DOT 4 brake fluids. Synthetic Lucas gear oil in the tranny and diff.

It is all in how you keep your car up. You can settle for mediocracy or you can have excellence. It is your choice. I choose Excellence.

 

^

 

I do 93 in the city, but if I'm going on a long trip on the highway I'll do 89 and be gentle, i get better mileage.

 

i run 93 in my vert i doubt it really shows a difference in performance but im not a cheap *** that wont spend the extra 2-3 dollars a tank for the better gas

 

so what is 105 octane? 105 octane and -5heptane?

 

Small thread jack;

Any local gas pump has reguler 87 octane, plus 89 octane, and 91 premium.

Where do find 93 octane?

And anyone who checks my vbgarage can see my car is moderatly upgraded and boosting 9-10 psi..

I'm currently running 89, should I switch to 91 or "93" for reliability? Performance?

And if there's a performance gain, is it worth it?

Gas ain't cheap yo!

 

From what I've read from Ted and Icemark: "Stock FCs, NA or Turbo, run fine on 87, modded Turbos should run 91 or better to help prevent detonation. Anything else in a stock FC is a waste of money, there are no gains in hp or anything. Lower octance ignites sooner and you want it to burn longer for best HP in a stock FC."

 

all depends on where you are.

Midwest is usually 87/89/93 or 87/89/92

There is one station where its 89/93, no 87, but the 89 same price as 87.

 

Unless youre knocking, you dont need higher Octane. IIRC lower octane gas actually has more energy in it, the higher octane gas wont ignite from compression as easily but ultimately has lower energy. However, you can still make more power from higher compression and advanced spark timing.

I dont know if you can tune the timing of a FCs stock ECM much, but the only advantage youd get from running 93 would be advancing the spark.

 

down here we have 87 89 93, no 91 round here...

 

Okay that solves my confusion about ratings. Here in Texas highest octane needed would be 91 while up north it could be 93... Makes sense.

Kinda curious about my personal fuel needs query, since I've never really thought about it before.

When I switched engines I was told to run at least plus from then on. I do, but I never considered that I may need supreme now.. Or might benefit a little at the very least. Sooo.

I like many gear heads believe a specific car is meant for specific octane ratings, and that anything else would be a waste(ie; civic ex running 91 all the time, etc)

Hence my intrique now, as this vehicle is the first most modded/nothing-like-factory I've owned.

While not wanting to make a mistake that could cost me my engine/car, myself like most everybody here is looking for that extra UMMPH!!

-Landon

PS. I love you guys

 

Fouls your plugs less? I'm nto tryign to be rude, but come on. A lower octane fuel will burn faster, and therefore will actually foul your plugs LESS than a higher octane fuel....there is something else at work here besides high octane gas.

--Alex

 

I run 100 octane sunoco.... ALL THE TIME

$4.59

My car is used only as a toy, and driven seldom.....

 

Like I said previously, say what you want. I know what happens in my cars because I am always in there once if not twice a day pulling things out checking around making sure everything is OK.

If you don't believe me I challenge you to do the test yourself . It cannot hurt only benefit knowledge. I don't really ever go by statistics. I go by what I observe happening to my vehicles and diagnose from there. I also do listen to statistics due to their relevancy and somewhat accuracy to a point.

Really I challenge anyone here to run the test yourselves. My Dad has the same conclusion so does everyone else I have shown my findings and plugs too. I wish I had a digital camera or I would post them up.

Hey that's cool to each their own. I'm just not a tight wad with cash even though I don't have much of it. When it comes to my cars nothing but the best is accepted. Performance wise.... I have noticed a difference when pulling hills and in the mountains as far as knocking with my N/A. My FD always has had '93 and sometimes aviation fuel for a treat for both. But I also do it for carbon residue control. I have noticed that when I burn higher octane fuels that there are significantly less carbon deposit build up in my engines. How do I know this? I pull the plugs get a mirror and shine a flash light into the hole.

Really I don't go by what I hear. I go by what I observe happening to my vehicles and make conclusions. I would say you guys should do the same and make conclusions for yourselves instead of arguing about it.

Do a test and post up the conclusions then compare and contrast the data collected.

 

Running high octane isn't hurting anything, and if you feel you can get extra power, have at it. But the theory behind it says that the lower octane should give you less fouling and more power.

Possibly the car's anti-knock sensor is making the mixture too rich with the lower octane fuel.

Aviation fuel is a bad thing. It is heavily leaded; even the so-called "low-lead" avgas has far more lead than leaded car gas ever did. Personally, I wouldn't run that stuff in my car unless I had no other choice.

BTW, the FC's manual warns repeatedly against running leaded car gas in your car. Running avgas is just asking for trouble, IMO.

--Alex

 

True True. But also leaded fuels clean and bust carbon out of your engine.

I get the unleaded aviation fuel not the low-lead kind.

 

Preignition= detonation. "One of the isomers, 2,2,4-trimethylpentane or isooctane, is of major importance, as it has been selected as the 100 point on the octane rating scale, with n-heptane as the zero point. Octane ratings are ratings used to represent the anti-knock performance of petroleum-based fuels (octane is less likely to prematurely combust under pressure than heptane), given as the percentage of 2,2,4-trimethylpentane in an 2,2,4-trimethylpentane / n-heptane mixture that would have the same performance. It is an important constituent of gasoline."
Quoted from wikipedia. You be the judge. I run 91. I will stick with it, because when I got the car, I was using 87. She would pop, and when I started using 91, no more popping..

 

And what color fuel would that be?