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Octane boosters?

13K views 15 replies 10 participants last post by  crowz 
#1 ·
I live in California where premium gas is only 91 octane, and I wish I could have 93 octane gas.

I'm thinking of buying a bottle of octane booster to add to a tank of 91 octane gas to fix that.

Will this cause any problems?

Will I notice any improvement?

Can anyone recommend a good brand?
 
#2 ·
Octane does not make power. Octane allows your motor to advance the timing further without knock. Buy a bottle of 104+ octane booster. Run it for a tank. If you can tell a difference keep doing so. If you cant you dont need it. More than likely 91 is fine.
 
#3 ·
octane booster does not raise the octane of the fuel and simply does not work. And reason why you only can get 91 octane is because it is actually 93 octane but California requires %15 ethanol to be added to fuel, this makes the rating drop to 91 because ethanol oxygenates the fuel.
 
#8 ·
octane booster does not raise the octane of the fuel and simply does not work. And reason why you only can get 91 octane is because it is actually 93 octane but California requires %15 ethanol to be added to fuel, this makes the rating drop to 91 because ethanol oxygenates the fuel.
Ethanol does indeed add oxygen to the fuel; this improves combustion and reduces ozone-creating emissions. However, ethanol actually RAISES octane, as pure ethanol has an AKI of 98.6.

What you mean to say is that adding ethanol reduces the energy content (BTU) of the gasohol blend (from wikipedia): "Octane ratings are not indicators of the energy content of fuels. (See Effects below and Heat of combustion). They are only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced. Ethanol BTUs can be compared with gasoline BTUs in heat of combustion tables."

Wikipedia has a pretty good article on octane: http://en.wikipedia.org/wiki/Octane_rating. In general, HakenTT is correct and octane boosters simply don't work, as high-octane gasoline has more "octane" molecules than regular. There's simply no way a small bottle can contain enough to significantly raise the octane rating very much.
 
#4 ·
I've never heard of them working. Once when we had a gas shortage due to a hurricane disrupting a refinery/pipeline to our area I had to buy 4-5 gallons of 87 octane b/c that was all they had. I added octane booster in hopes that it would run better. It may have run less crappy (never ran 87 before so no baseline), but it certainly didn't run at all like the premium I normally run.
 
#5 ·
Thanks, guys. I'll guess I'll settle this empirically by following Crowz' suggestion and trying 104 (which someone else recommended to me as well). If it works, great, and if it doesn't, I'll add myself to the ranks of skeptics. My main concern was that I not be doing some damage to my engine with this, and it sounds like I won't be.
 
#7 ·
Octane booster does work. Its actually required on some gas generators to keep them from rattling like mad with cheap gas (ran into this during some storms for example). The only real "test" you as a consumer can actually do is with a motor that is using fixed timing and doesnt have a knock sensor and a computer adjusting.
 
#9 ·
http://www.nicoclub.com/archives/gasoline-octane-myths.html

Our cars run better on 91 because the engines are a high compression design. This requires a slower burning fuel to prevent detonation/knock, which is harmful for your engine. Non-M cars can adapt to a slightly higher octane fuel, but not much higher. M-cars can adapt to a lot more octane.

I've done track days in the 105+ degree heat of summer on 91 pump gas and never experienced any knocking or power loss. I've mixed in a half tank of 100 as a "let's see what happens" and didn't notice any performance difference. Certainly not enough to justify the $8/gallon price.

My high compression carbureted motorcycle has a love hate relationship with 91 pump gas. At low elevations like where I live, it needs more to make power. I've run 100 in it with great results, but it's ignition module is not adaptive like the one in our cars. At high elevation, 8k feet and above, she'll run great on 89.

Now, the empirical test

http://youtu.be/zKxJfXfD6mg
 
#14 ·
Yep. Waste of money. Also, these M54 engines are not really that high in compression. Mine is 10.2 which is average among engines these days. Truth be told, they run fine on mid grade gas (89). If you demand that last bit of performance and don't mind paying for it then by all means buy the highest octane gas you can get. The engine management system will automatically adjust the timing to take advantage of the higher octane.
 
#10 ·
Either it's in my head or it does actually work. I used the 104+ for a few tanks to see if my mpgs went up, and it was a success. In my opinion, I believe they work. I put 93 in it every fill up with a bottle and my mpgs went up, which was my goal. I'd try it out if I were you. It hasn't hurt my engine. Hell I've owned mine for 3+ years with 153000 miles and I've yet to even see the check engine light on. Crossing my fingers
 
#13 · (Edited)
I invite the OP to enter in the data into this philosophical BMW psychology thread ...
- Research into how our Myers-Briggs personality profile affects what BMW motor oil, coolant, and gasoline religious dogma decisions we should recommend when people ask which fluid to use (1)

See also:
- How to better understand the piezoelectric knock sensor operation (1) & how long does it take the BMW knock sensors to adjust the fuel trim based on the gasoline octane rating of the fuel used (1) & what gasoline octane should we use (1) & how do they measure octane ratings around the world (1) & where is "The Gasoline FAQ" & what are the top-tier gas stations (1) & how large is the fuel tank and reserve (1) & how much gas should be left to cool the fuel pump (1) & how can we siphon the fuel out of the tank (1) & what is the cost differential between 87 & 91 octane AKI anyway (1) & whats all this about techron (1) & what are the religious dogmatic camps when it comes to BMW fuel choice (1) & how accurate are our mpg calculations (1) & compendium of BMW emission smog test results (1) & what states make it illegal to sell a car "as is" that won't pass smog or that have an SES/CEL light lit at the time of sale (1)
 
#15 ·
Update: I tried a bottle of 104+ when I filled the tank a few days ago. I've used about half the tank since then. I haven't noticed any difference in power or fuel economy.

I'm not saying it doesn't work in some engines, but it doesn't seem to make a difference in mine.

It was worth a try.
 
#16 ·
Like I posted unless your hitting the advance limit from knock your not going to notice any difference. 93 octane for sure is plenty from what I can tell and Id think 91 would probably be ok too. Now run 87 for 2 tanks worth and drop it in there and THEN you will see a difference Id bet. But to me its easier to just run the right octane fuel to start with.
 
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