Added Octane

Stock4Evr · 03-30-2018, 03:33 PM

Do those octane additives actually do anything or are they just there to attempt to make you feel as if you are getting a slight boost?

atr_hugo · 03-30-2018, 04:39 PM

Octane is a term used to designate a fuel's ability to not detonate, 'knock', prior to the spark being applied. Low octane numbers mean less anti-knock capabilities, higher octane numbers mean more resistance to knock. The lower the octane, the less compression you can apply to fuel and air.

You would want to increase octane if you increase the compression ratio - and that includes increasing boost. If the car is stock, there are no benefits to increasing octane (beyond psychological, that is ; -).

BimmerAg · 03-30-2018, 05:11 PM

Yep, what atr_hugo said. Fuel octane is only increases performance if you tune to take advantage of it. The stock tune will be optimized for stock boost and spark timing and won't be taking advantage of the added knock resistance for higher octane fuel.

I've also heard that those octane boosters don't really raise the octane that much. Maybe from 93 to 94 for example if you get a good one. You're better off buying actual race gas if you really want higher octane fuel. Ethanol also has higher octane than regular gas, so if you have a tune that's developed for a partial ethanol mix like E30, then you can take advantage of the increased octane from that instead of needing race gas.

asiflicious · 03-30-2018, 05:42 PM

Quote:

Originally Posted by BimmerAg

Yep, what atr_hugo said. Fuel octane is only increases performance if you tune to take advantage of it. The stock tune will be optimized for stock boost and spark timing and won't be taking advantage of the added knock resistance for higher octane fuel.

I've also heard that those octane boosters don't really raise the octane that much. Maybe from 93 to 94 for example if you get a good one. You're better off buying actual race gas if you really want higher octane fuel. Ethanol also has higher octane than regular gas, so if you have a tune that's developed for a partial ethanol mix like E30, then you can take advantage of the increased octane from that instead of needing race gas.

Would it be a good option for us poor souls that only have access to 91/92 octane?

Pig Farmer · 03-30-2018, 06:18 PM

So I'm just posting what I have done in the past, but you need to decide kwhether it is right for you...

When I had my tuned N54/135i, I could feel the timing being pulled (significantly) on hot humid days in S.FL. To correct the problem, I would mix 2 gallons of xylene, 4oz of Marvel Mystery Oil and fill up the rest of the tank with 93 octane. The car never pulled timing again. I personally had no issues with the fuel line, fuel pumps, or injectors while running this mix. If you decide to try this, wear gloves and DON'T get the xylene on your paint. You can pick up a gallon of xylene at Home Depot for about $20 in the paint section.

Stock4Evr · 03-31-2018, 10:06 AM

Thanks to one and all responses. I knew it was not to late to learn something.

TT1351 · 03-31-2018, 11:09 AM

Sunoco sells unleaded high octane fuel and for some reason even offers it in a 10% alcohol version. To me that is a sure fire way to increase octane levels. All the additives that claim a 4 point boost, really should call it a .4 point boost, so a 4 point boost to 91 octane doesn't bring it to 95 octane, but slightly brings it 91.4 octane. I don't know where I read this info, but I did see it somewhere.

03-30-2018, 03:33 PM	#1
Stock4Evr RetNavSpook 67 Rep 398 Posts Drives: 2012 135i - 2016 320i Join Date: Jan 2014 Location: Canyon Lake, Texas iTrader: (0)	Added Octane Do those octane additives actually do anything or are they just there to attempt to make you feel as if you are getting a slight boost?
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03-30-2018, 04:39 PM	#2
atr_hugo No longer moderate 325 Rep 4,401 Posts Drives: '13 135i Join Date: Jun 2007 Location: - iTrader: (0)	Octane is a term used to designate a fuel's ability to not detonate, 'knock', prior to the spark being applied. Low octane numbers mean less anti-knock capabilities, higher octane numbers mean more resistance to knock. The lower the octane, the less compression you can apply to fuel and air. You would want to increase octane if you increase the compression ratio - and that includes increasing boost. If the car is stock, there are no benefits to increasing octane (beyond psychological, that is ; -).
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03-30-2018, 05:11 PM	#3
BimmerAg Lieutenant 425 Rep 545 Posts Drives: 2011 135i Join Date: May 2017 Location: San Antonio, TX iTrader: (0)	Yep, what atr_hugo said. Fuel octane is only increases performance if you tune to take advantage of it. The stock tune will be optimized for stock boost and spark timing and won't be taking advantage of the added knock resistance for higher octane fuel. I've also heard that those octane boosters don't really raise the octane that much. Maybe from 93 to 94 for example if you get a good one. You're better off buying actual race gas if you really want higher octane fuel. Ethanol also has higher octane than regular gas, so if you have a tune that's developed for a partial ethanol mix like E30, then you can take advantage of the increased octane from that instead of needing race gas. __________________ 2011 BMW 135i ///M-Sport, DCT Bilstein B12 kit, Dinan camber plates, M3 front control arms, Whiteline poly RSFB, MHD Stage 1, cp-e Charge Pipe, H&R Front sway bar, BMW performance diffuser
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03-30-2018, 06:18 PM	#5
Pig Farmer Major 340 Rep 1,293 Posts Drives: E92M Join Date: May 2010 Location: Florida iTrader: (0)	So I'm just posting what I have done in the past, but you need to decide kwhether it is right for you... When I had my tuned N54/135i, I could feel the timing being pulled (significantly) on hot humid days in S.FL. To correct the problem, I would mix 2 gallons of xylene, 4oz of Marvel Mystery Oil and fill up the rest of the tank with 93 octane. The car never pulled timing again. I personally had no issues with the fuel line, fuel pumps, or injectors while running this mix. If you decide to try this, wear gloves and DON'T get the xylene on your paint. You can pick up a gallon of xylene at Home Depot for about $20 in the paint section.
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03-31-2018, 10:06 AM	#6
Stock4Evr RetNavSpook 67 Rep 398 Posts Drives: 2012 135i - 2016 320i Join Date: Jan 2014 Location: Canyon Lake, Texas iTrader: (0)	Thanks to one and all responses. I knew it was not to late to learn something.
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03-31-2018, 11:09 AM	#7
TT1351 Captain 508 Rep 929 Posts Drives: 135, GTS, E30 M3+ Join Date: Dec 2008 Location: Massachusetts iTrader: (2)	Sunoco sells unleaded high octane fuel and for some reason even offers it in a 10% alcohol version. To me that is a sure fire way to increase octane levels. All the additives that claim a 4 point boost, really should call it a .4 point boost, so a 4 point boost to 91 octane doesn't bring it to 95 octane, but slightly brings it 91.4 octane. I don't know where I read this info, but I did see it somewhere.
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