[fourdirtyfive]

Are there any noticeable HP gains switching from 91 to 100 octane? Found two gas stations that offer 100 at the pump sorta near me, wondering if it'll make a noticeable difference in engine performance on my '15 435i MPPK. Anybody have experience/knowledge on this?

[COKen]

I don't think you would see any difference unless you had mods on your car which could take advantage of the additional octane. Your car, from BMW, is setup to run best with the recommended octane.

[rlmesq]

If you don't hear knocking under acceleration, you don't need a higher octane rating. It isn't going to make your car faster or better performing.

[fourdirtyfive]

Originally Posted by rlmesq

If you don't hear knocking under acceleration, you don't need a higher octane rating. It isn't going to make your car faster or better performing.

Thanks for the response. If I were to install a Jb4 and set it to Map 5 (automatically determines boost based off fuel, temp, etc.), I would see a noticeable gain then?

[chiefneil]

Sounds like a huge waste of money. If you're an experienced track driver then maybe you'd notice and appreciate the difference on a track day. But for daily driving when you're not at max acceleration I can't see how it would make a difference.

[fourdirtyfive]

Originally Posted by chiefneil

Sounds like a huge waste of money. If you're an experienced track driver then maybe you'd notice and appreciate the difference on a track day. But for daily driving when you're not at max acceleration I can't see how it would make a difference.

that was my thought, thanks for clarifying.

[CalCarNut]

I've been tempted to throw in a tank of 100 as well just to see if it feels different. I know at the track when I've run 100 in my other car (not stock), it helped bring the ET down and MPH up. I'm curious to see if the higher octane helps my GC, given that it's flash tuned, in terms of seat of the pants etc. Guessing it'll run a LITTLE better but worthy of the $ difference, probably not lol.

[Billfitz]

Originally Posted by fourdirtyfive

Are there any noticeable HP gains switching from 91 to 100 octane?

Higher octane is less volatile than lower octane, so it doesn't give more HP. What gives higher HP is higher compression and boost, which may require higher octane to prevent knocking. It would take a full blown race engine to need 100 octane.

[CalCarNut]

Originally Posted by Billfitz

Higher octane is less volatile than lower octane, so it doesn't give more HP. What gives higher HP is higher compression and boost, which may require higher octane to prevent knocking. It would take a full blown race engine to need 100 octane.

Is this why your 'friend' runs 89 octane? Higher HP?

[Billfitz]

Originally Posted by CalCarNut

Is this why your 'friend' runs 89 octane? Higher HP?

Higher IQ.

[CalCarNut]

Originally Posted by Billfitz

Higher IQ.

[BEAR-AvHistory]

Some dyno tests I did a while back on a stock 335is maxed out around 94.5 octane. With JB4/COBB stacked tunes & a few other things it ran better on pure 100.

Point is the engine can't use any higher octane than it can use. Going high in the engine can't use it just wastes money.

You might do better with 93 the premium in NC & most east coast states but I really doubt much more will do anything..

If you are in a 91 state & want to play mix 91 & 100 to get different blends of octane. I had a fast street tune that used 50/50 mix of 93/100 for about 96 octane.

[lens]

Originally Posted by fourdirtyfive

Are there any noticeable HP gains switching from 91 to 100 octane? Found two gas stations that offer 100 at the pump sorta near me, wondering if it'll make a noticeable difference in engine performance on my '15 435i MPPK. Anybody have experience/knowledge on this?

91-94 is fine for a stock car.

But if you go FBO or add a tune like JB4 or BM3, then 100 octane would absolutely help. Better octane=less knock and better timing control. You can up the boost safely depending on your map or OTS map.

[Vegetable]

Originally Posted by BEAR-AvHistory

Some dyno tests I did a while back on a stock 335is maxed out around 94.5 octane. With JB4/COBB stacked tunes & a few other things it ran better on pure 100.

Point is the engine can't use any higher octane than it can use. Going high in the engine can't use it just wastes money.

You might do better with 93 the premium in NC & most east coast states but I really doubt much more will do anything..

If you are in a 91 state & want to play mix 91 & 100 to get different blends of octane. I had a fast street tune that used 50/50 mix of 93/100 for about 96 octane.

BEAR, does your 440i with MPPSK feel significantly faster than your 435i with MPPK?

[jgoens]

Here's my opinion: I have JB4 and DP. I regularly use e85 and have tried a full tank of 102 as well as a mix of 102, E85 and 91. I felt like everything was the same and therefore it is more economical to just use e85. When I did the whole tank of racing I ran map 7 and it was fast but I can't say it was more intense than 4.5 gallons of e85, the rest 91 on map 5.

Of course I am just talking butt feel and conditions can be different from day to day. And since the question is regarding the Mppk it might be irrelevant, but that is my experience on the octane effect on power.
I also did this with my e90 and had the same perceived results.

[stormlv]

Originally Posted by rlmesq

If you don't hear knocking under acceleration, you don't need a higher octane rating...

IIRC the knock sensors in our cars should detect and correct anything way before the driver realizes there's an issue.