100 Octane

[thepuya]

I saw this at the gas station last week. I was VERY tempted, but wasn't ready to fork over the $100+ to fill up the tank.

Has anyone tried 100 octane gas?

The gas station is in West Los Angeles, and the 100 octane seems like a permanent fixture.

[ipsofacto]

I did once .. got no difference compared to 95

[OrangeOne]

I have been pumping Shell's V-Power, which is rumored to be around 107 RON. I am not really sure if it does help the engine but i will give my Z4 the best

[///carbon]

i always put 100 octane...

no difference at all.

but i feel better. hehe

[mcbeee]

Remember that 100 octane in the USA & Canada is not the same as 100 octane in Europe and elsewhere..... 100 in Europe is roughly equivalent to 93 or 94 over here. I've seen posts that go into great detail on how the calculations are done but I'm not going looking for them right now.

Ciao

[siscobmw]

wellcome in our world....here in Italy we have 100 octane fuel,by shell firstly, since 2001....
and I notice the diference under my right foot, not only inside my wallet....
Francesco

[Silver-Bolt]

Octane is a often misunderstood. The higher the octane rating the slower the fuel burns. High octane fuel will not produce more power. It will however allow for a higher performance tune which will make more power. On a stock vehicle high octane fuel will likely produce less power. On a tuned vehicle it will allow for higher boost level and increased timing which in turn make more power.

[mcbeee]

I use 94 octane in my car and belive it is roughly equivalent to the 99 or 100 available in Europe. Our normal Premium is 91 or 92 depending on which gas station you use. Better performance for sure but no improvement on fuel economy. The octane boost of 2 points from 92 to 94 is mostly due to a small mix of ethanol in the fuel (less than 10%).

[ttuner]

unless your car is tuned for it, you will not notice any difference and you will be wasting you money. stick with 91-93 oct.

if your running a chip/tune that is made for 100 oct, then you will see improvement. rather than wasting 100 bucks every fill up, look into meth injection. i ran meth on my audi on a program tuned for it and it was great (ran 90oct on a 93oct program). it was only like 10 bucks for a gallon of meth, then you mix it with water. would last about 2 fill ups.

[teagueAMX]

I think the operative words are potential performance. Allow me to explain.

Octane by itself does not produce power. As mentioned, it is a combustion inhibitor and as such it allows the use of higher compression in an engine that would normally suffer pre-detonation. Keep in mind that a turbocharged engine is a very high compression unit. Most modest beasts of burden, especially your older Fords, Chev, etc., have a static compression ratio for a normally aspirated engine of 8.5:1 designed to run on “regular” gas. Engine management computer have helped so now it’s possible to run higher compression ratios on “regular” fuel. Keep in mind that the n54 has a static compression ratio of 10.2:1, but the dynamic compression ratio climbs dramatically due to forced induction of turbocharging.

An issue with lower octane gas is that it tends to burn hotter (i.e, lack of the combustion inhibitor) so the engine is equipped with octane sensors. When it detects a lower octane fuel the sensor trigger the engine management computer to alter the air fuel mixture to a less optimal ratio to prevent a too-lean mixture resulting from the hotter combustion. This means less performance.

Because of the heat and the resulting combustion chamber hot spots that result, a phenomenon called pre-detonation occurs in the engine's combustion chamber that ignites the air fuel mixer before it's optimal point in the combustion cycle. It also creates a cascading detonating effect of multiple combustion events in the same cycle. During pre-detonation, the engine will produce an abnormal vibration sometimes referred to as a "knock", which is quite detrimental to your engine. BTW - most of the time can't hear the knock. The engine is equipped with sensors that detect the knock and retard the ignition point accordingly. This means less performance.

So to say that a higher octane doesn't increase performance is in fact a true statement. But it also means that your engine will not run at its full potential as a result of all the adjustments the engine management computer has to make to prevent damage to your engine. Lower octane cuts your performance at levels most of us never utilize but your engine is deigned to provide under ideal conditions.

The moral to the story: friends don't friends use low octane gas in a high compression engine - YOUR BMW!

[m6pwr]

This topic has been discussed endlessly on other forums, particularly the e46 m3 forums. There was a Car & Driver article related to this topic that featured an m3. This was about the time that CA and some other states had reduced the octane of high test from 93 to 91 AKI. The gist was that the m3 ecu was optimized to run on 93, but would run fine on 91 (and even less, down to a 87 or 89), but would lose a little power since the (very advanced) ecu would continually and instantaneously roll back ignition timing to compensate and avoid detonation. Something like that. The same may apply to our n54 ecu. If its true, you can get a blend of 91 and 100 to get 93; about 8 gals of 91 mixed with 2 gals of 100: http://www.runyard.org/jr/CFR/racinggas100.html. If you really want to go to all that trouble. Nevertheless, I remember many posts from m3 owners who would track their cars and fill up on 100 octane racing gas at the track and insist that they could feel a significant increase in power and smoothness. Can our n54 be any smoother?

[teagueAMX]

Points well taken and nice chart. And I think the potential is on the high of the performance curve. I've suggested in the past a dose of octane boost for those occasional Saturday or Sunday canyon carving events.

[zeez_Dubai]

there was an episode in topgear which involved a turbo charged car.

3 different octane rated fuel and 1 dyno.

they noticed at the end that torque went up by 3-4% and hp 5% or so

youtube time

[Dr Stig 2]

Originally Posted by zeez_Dubai

there was an episode in topgear which involved a turbo charged car.

3 different octane rated fuel and 1 dyno.

they noticed at the end that torque went up by 3-4% and hp 5% or so

youtube time

yep

same episode compared a boring sedan and an Evo (mitsubishi). The regular car gained nothing, the Evo gained a significant improvemnt in engine power.

[Silver-Bolt]

If you want to occasionally increase your octane without paying for race fuel add Toluene to your tank. Can be purchased at any paint supply store. It is the chemical that makes octane. I have a mix ratio chart if anyone is interested. I use it when I take my Lightning to the drags. Allows my to run more timing advance and more boost. 11.01 @ 123mph the best so far with it. 11.3's on the lower octane tune.

[teagueAMX]

Originally Posted by Silver-Bolt

If you want to occasionally increase your octane without paying for race fuel add Toluene to your tank. Can be purchased at any paint supply store. It is the chemical that makes octane. I have a mix ratio chart if anyone is interested. I use it when I take my Lightning to the drags. Allows my to run more timing advance and more boost. 11.01 @ 123mph the best so far with it. 11.3's on the lower octane tune.

I'm interested in that chart. Thanks

[laz4]

So would you say that 100 octane would make a noticeable difference on a 35i considering the twin turbo engine?

[Gunzaro]

On my 35is with ESS tune I notice a difference between 98 and 100 octaine (ethanol blend). With 100 octaine I loose traction a bit more even in Sport+ mode (traction light flashes) and it actually makes me slower when this happens!!!

So although I may get more power with 100, I think 98 might be better till I get new tires!!

Takes a few runs for the ECU to adapt with timing.

[redhot]

Originally Posted by Silver-Bolt

If you want to occasionally increase your octane without paying for race fuel add Toluene to your tank. Can be purchased at any paint supply store. It is the chemical that makes octane. I have a mix ratio chart if anyone is interested. I use it when I take my Lightning to the drags. Allows my to run more timing advance and more boost. 11.01 @ 123mph the best so far with it. 11.3's on the lower octane tune.

I have been thinking of adding acetone to my 91 costco gas. Will it be ill-advised to add acetone to our N54? I know it acts as a octane booster similar to Toulene however I also read somewhere that it helps with cleaner plumbing as some injector cleaners have it ?

[laz4]

My question was for a non tuned twin turbo as in a stock 35i. We have established that a tuned engine will benefit from a higher octane. We have only conjecture based on comments about the 35i engine.

[Gunzaro]

100 oct should enable you to get the most power out of your N54 engine as it will help prevent detonation and allow the ECU to adapt and most effectively advance timing. How much power = you will need to dyno.