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BMW explains using lower Octane gasoline

This is an interesting read, it is dated before the twin scroll turbo days, so it is unclear if the advice still applies to N20/N26 in F30:

http://forum.roadfly.com/threads/12615839-BMW-explains-using-lower-Octane-gasoline

"Thomas Plucinsky, BMW Product and Technology Communications Manager told us all BMW engines are designed to run on 91 octane. All performance testing, including EPA emissions and fuel mileage, is done with 91 octane. However, though BMW is all about performance, their motors will run on 89 or 87 octane without damage. The knock sensors pull the ignition timing back and eliminate detonation. There will be a loss of power and a decrease in fuel mileage, but the size of the horsepower loss and the increase in fuel consumption depends upon many factors, such as ambient temperature, exact formulation of the fuel and driving technique, so BMW does not offer any estimates for operation on lower grade fuels. One not so obvious concern, Mr. Plucinsky noted, is the type and quality of additives the gasoline companies include in the fuel. Premium gasolines may have better additive packages which are more effective keeping fuel systems (particularly injectors) clean and working efficiently, than those in regular grade fuels or off-brand products. Using lower octane or off-brand fuel could be degrading the fuel system over time, setting you up for a repair bill down the line."

The last point of the quote is to use gasoline with good additive packages, but implies premium gasoline has better additive packages than regular gasoline, however top tier retailers(e.g. Costco) advertise all their grades carry the same additive packages.
 

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BMW's first choice for "top tier" has changed since that originally was stated however the basic point remains the same. I have been a Shell V-Power 93 customer since Sunoco 94 was discontinued in my area years ago. I have 93 file tunes on my vehicles so I always have to use 93 but even without tune I go for 93 when available or just a few pumps of 91. The honest answer I can't tell the difference when it's filled with either except slightly better mpg with the 93.
 

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Thomas Plucinsky, BMW Product and Technology Communications Manager told us all BMW engines are designed to run on 91 octane. ...However, though BMW is all about performance, their motors will run on 89 or 87 octane without damage.
And that quote is still applicable. Buy 93 octane if it makes you feel better, otherwise follow the owners manual and buy 91 or 89 octane from a reputable gas station that takes care of their equipment. Then move on to more important things.
 

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BMW CCA 1405
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... top tier retailers(e.g. Costco) advertise all their grades carry the same additive packages.
Costco's regular and premium grade have the same minimum amount of additives to qualify for Top Tier.

Shell is Top Tier, but their regular 87 does not have the additives that Shell V-Power NiTRO+ Premium 93 has.
Shell V-Power NiTRO+ isn't just reinventing premium gasolines, it's reinventing the premium gasoline category.
http://www.shell.us/motorist/shell-...tro-plus-premium-gasoline/under-the-hood.html
 

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Discussion Starter · #7 · (Edited)
Costco's regular and premium grade have the same minimum amount of additives to qualify for Top Tier.

Shell is Top Tier, but their regular 87 does not have the additives that Shell V-Power NiTRO+ Premium 93 has.
That is good to know about Shell 87 versus 93. That probably means the Shell 87 still has the minimum additives to be top tier, but the Shell 93 has additional additives, right?

In one service visit the loaner desk person filled up an empty tank with 87(the station was next door and I hopped on to save time) on a 328i loaner. It felt like the ECU turned off the turbo or something. The sport was like comfort, and comfort became eco, and eco had zero throttle response. After half tank I put back in Costco 91(or probably any 91), and the car came back to life again. :)

Hmm, how many dismiss N20/N26 as inadequate while the loaners/test drives run on 87?
 

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That is good to know about Shell 87 versus 93. That probably means the Shell 87 still has the minimum additives to be top tier, but the Shell 93 has additional additives, right?...
Yes, Top Tier is given to an entire brand, not a grade.
All of Shell is Top Tier, but Shell 87 does not have the extra additive V-Power NiTRO+ that Shell Premium 93 has.
 

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Discussion Starter · #14 · (Edited)
An experiment was conducted the past 2 days to test out the 89 AKI min. The previous full tank was Costco 91. 2 days ago, 9 gal of Costco 87 were added, to get effective 88.75 AKI. The ECU recognized that fairly quickly and the mpg dropped from usual 25-26mpg to 20-22mpg, based on trip computer(reset at fillup).

After 45 miles, 2.5 gals of Costco 91 were added yesterday, for an effective 89.1 AKI. The mpg jumped immediately to 27mpg, and on highway stretches up to 30+mpg (shown on trip computer, reset at fillup).

The 88.75 AKI was sluggish, just like past experience with loaner + full tank 87 AKI. It looks like sensor is so sensitive that it quickly readjust when AKI changes across the 89 threshold. It is interesting that the 89.1 AKI can provide such a dramatic change in mpg, and the power difference between the 88.75 and 89.1 is noticeable. BTW full tank 91 AKI on the same routes seldom yields above 26-27mpg, and the engine output feels stronger than 89.1.

It would be interesting to try out 93, although none of the top-tiers carries that.
 

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An experiment was conducted the past 2 days to test out the 89 AKI min. The previous full tank was Costco 91. 2 days ago, 9 gal of Costco 87 were added, to get effective 88.75 AKI. The ECU recognized that fairly quickly and the mpg dropped from usual 25-26mpg to 20-22mpg, based on trip computer(reset at fillup).

After 45 miles, 2.5 gals of Costco 91 were added yesterday, for an effective 89.1 AKI. The mpg jumped immediately to 27mpg, and on highway stretches up to 30+mpg (shown on trip computer, reset at fillup).

The 88.75 AKI was sluggish, just like past experience with loaner + full tank 87 AKI. It looks like sensor is so sensitive that it quickly readjust when AKI changes across the 89 threshold. It is interesting that the 89.1 AKI can provide such a dramatic change in mpg, and the power difference between the 88.75 and 89.1 is noticeable. BTW full tank 91 AKI on the same routes seldom yields above 26-27mpg, and the engine output feels stronger than 89.1.

It would be interesting to try out 93, although none of the top-tiers carries that.
Thank you for posting your findings. However I am highly skeptical. There is of course no scientific validity to it and none of us have a repeatable way to test fuel economy. Knowing the average speeds of the two tanks would help along with the weather conditions. My own personal anecdotal experience is that I notice almost no change in fuel economy between 91/93 octane fuel and 89 octane. My driving habits are highly variable so they are probably even less scientific than yours. As far as acceleration, my butt dyno can't tell a difference. Even BMW says it's just a few HP.
 

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Discussion Starter · #16 ·
Thank you for posting your findings. However I am highly skeptical. There is of course no scientific validity to it and none of us have a repeatable way to test fuel economy. Knowing the average speeds of the two tanks would help along with the weather conditions. My own personal anecdotal experience is that I notice almost no change in fuel economy between 91/93 octane fuel and 89 octane. My driving habits are highly variable so they are probably even less scientific than yours. As far as acceleration, my butt dyno can't tell a difference. Even BMW says it's just a few HP.
It is good to know your user experience of 91/93 and 89 are similar(both mpg and power). Yes the average mph's are important but they were not noted, so any observations made on mpg are not really inconclusive as the data is incomplete.:cry: The interesting point to me is that the threshold of 89 AKI generates a noticeable drop of mpg even at highway speed, so sensors are working as expected.

Online search does say a local few stations(including a 76) have 93(and even 100), I may give it a try, or maybe not. :)
 

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It is good to know your user experience of 91/93 and 89 are similar(both mpg and power). Yes the average mph's are important but they were not noted, so any observations made on mpg are not really inconclusive as the data is incomplete.:cry: The interesting point to me is that the threshold of 89 AKI generates a noticeable drop of mpg even at highway speed, so sensors are working as expected.

Online search does say a local few stations(including a 76) have 93(and even 100), I may give it a try, or maybe not. :)
I don't know if you have Sunoco stations in your area but they carry 87, 89, 91 and 93 octane. I don't think they are Top Tier rated but I've never had an issue. I filled up today with 91 octane Sunoco.
 

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Discussion Starter · #18 ·
I don't know if you have Sunoco stations in your area but they carry 87, 89, 91 and 93 octane. I don't think they are Top Tier rated but I've never had an issue. I filled up today with 91 octane Sunoco.
In fact the local 76 mentioned carries Sunoco GT 100 unleaded at the pump. Sunoco 110 104, 112 are also available but probably would require containers.
 

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89 is fine, 91 is recommended, 93 is a waste of money.
 
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