Octane

[Johninjax]

I was recently told by my dealer that even though our cars require 91 octane they will run better on 89 than 93 ( 87,89,93, are what's available in my area). The rational being that the cars computer can better compensate for two points lower better than two points higher. This is supposedly been confirmed by BMW execs however this is not the company line,any feedbeck would be welcome.

Thanks

 

[Kirby]

He's full of crap. A car that is designed to run at a specific octane level WILL NOT run better on lower octane. Running 93 in a car that is designed for 91 will just allow it to perform at or around the 91 octane level.

 

[///M SPEED]

I agree with Kirby here. You should find yourself a different dealer if this is the advise he/she/they are giving you. The car runs off the octane level, which means higher = better....

 

[Big Daddy]

I agree with Kirby and Scott, where did this clown get his/her information?

 

[newguy]

In every ECM there are "knock sensors". They identify detonation which occurs within the engine, and retard timing to ensure it does not happen. Lower octane means a lower threshold for detonation, which causes the ECM to retard the timing in an engine. This results in lower performance...higher octane means a higher threshold for detonation, and will allow the timing to advance..this will allow better performance...hope this helps. It is a rather simplistic view of what goes on in the engine..

 

[Andre]

My ZHP definitely performs less with less octane.

On the other hand, it performs better with even more. In fact it LOVES octane. If I fill up with Sunoco 94, then add two bottles of STP octane boost, the car thanks me. Definitely more pull, with a smoother delivery.

 

[newguy]

Hey Andre,great minds think alike...I use 94 also...We blend it at the refinery I work at....as an octane "enhancer" I add 99.9% pure toluene..the last octane I saw on this was about 130 or so.(about 3-litres or so to a tank). The car eats it up...have fun

 

[jrt67ss350]

Hey Andre,great minds think alike...I use 94 also...We blend it at the refinery I work at....as an octane "enhancer" I add 99.9% pure toluene..the last octane I saw on this was about 130 or so.(about 3-litres or so to a tank). The car eats it up...have fun

Hahaha! That's awesome. Spoken like a true chemist!

 

[Kirby]

Hey Andre,great minds think alike...I use 94 also...We blend it at the refinery I work at....as an octane "enhancer" I add 99.9% pure toluene..the last octane I saw on this was about 130 or so.(about 3-litres or so to a tank). The car eats it up...have fun

Hmm, according to European Car, adding 30% touluene to 91 octane gas results in an R+M/2 Octane rating of 95, and destroys the engine components. Sounds to me like it eats the car up!

 

[Big Daddy]

Oops there goes that theroy! Too much octane booster is a bad idea.

 

[Andre]

STP Octane Boost uses MMT, which doesn't appear to have the same issues.
http://www.epa.gov/otaq/regs/fuels/additive/mmt_cmts.htm

 

[PhatBimmer]

I thought Octane boosters were just more of a form of alcohol which is corrosive?

 

[Zchild]

Hey there Bimmer-dreamers and Gearheads, most excellent exchange of ideas, facts, asumptions and information. I may be prematurely reading into these many and varied posts, but the pattern I'm getting is that I should personally look at the purchase of a Cold Air Intake, Proformance Chip and High Flow Exhaust and just leave the Octane Boost alone because of potential damage to my emission and on board computer systems. I am just looking at getting more Horse Power from my bimmer vice more octane from my fuel. Just my two and a half cents... Happy Motoring...
[driving2]

 

[ThatOneGuy]

Your car will run on lower octane fuel, just not as well. The computer will retard the timing to protect the engine from detonation. If it were my car, I'd use whatever was the highest octane fuel available at the pump.