[Roki_014]

there is a guy at my work, who worked at a gas station while going to school, and he said the owner of the gas station would mix grades, so the 93 would actually be a mix of 87+89 or just one of the others, that way he would make the money on the difference plus whatever they get, I will check with him later what gas station that was, i know its somewhere by IIT

[Michael Schott]

Originally Posted by Monkeycmonkeydo

So an honest question here... If a shop specialized in 100 octane how much more performance would I get in my 335? Would I notice the car driving better than say 91?

Unless you added a modification that can allow the engine to make more power at higher octane, none. the stock engine makes maximum power with 91 octane fuel in the US. The engine computer will not advance the timing to compensate for the higher octane fuel.

[Monkeycmonkeydo]

Originally Posted by Michael Schott

Unless you added a modification that can allow the engine to make more power at higher octane, none. the stock engine makes maximum power with 91 octane fuel in the US. The engine computer will not advance the timing to compensate for the higher octane fuel.

Interesting. Thanks

[Elk]

Originally Posted by Roki_014

there is a guy at my work, who worked at a gas station while going to school, and he said the owner of the gas station would mix grades, so the 93 would actually be a mix of 87+89 or just one of the others, . . .

Every state has a regulatory agency that checks for this, as well as pump accuracy. Hopefully he will get caught.

[Elk]

Originally Posted by Michael Schott

Unless you added a modification that can allow the engine to make more power at higher octane, none. the stock engine makes maximum power with 91 octane fuel in the US. The engine computer will not advance the timing to compensate for the higher octane fuel.

Absolutely correct (you knew this).

Additionally, you may experience decreased performance; when a high octane fuel's resistance to detonation gets too high it effects combustion, wave front development, etc. in an engine not designed for it.

[woderd]

I would put in 85 if they had it.

[MarkyMarkOz]

My only input is:

1. RTFM that is localised for your country.

2. 'Premium' I think is the universal word here. For example, here in Australia we typically have readily available 91, 93, 95 and 98 Octane. 91 is usually a 10% ethanol blend. the 'Premium' fuels are typically the 95 and 98. Now in Australia we unfortunately have poorer quality fuel in the lower end of the spectrum, so I run only 95 or 98. Additionally and importantly, across both my v8 landcruiser and the 328, I have run measurements in fuel consumption and because of all the nice additives I get a much higher mileage which brings the total cost back to almost being competitive with running the 91. Also, the additives list in the 98 seems to keep my hi mileage landcrusier running more smoothly and better power (seat of the pants measurement on that last point).

[Elk]

This makes sense. Oz measures octane by RON resulting in octane rates ~5 points higher than AKI in the U.S.

[RPM90]

Originally Posted by MarkyMarkOz

My only input is:

1. RTFM that is localised for your country.

2. 'Premium' I think is the universal word here. For example, here in Australia we typically have readily available 91, 93, 95 and 98 Octane. 91 is usually a 10% ethanol blend. the 'Premium' fuels are typically the 95 and 98. Now in Australia we unfortunately have poorer quality fuel in the lower end of the spectrum, so I run only 95 or 98. Additionally and importantly, across both my v8 landcruiser and the 328, I have run measurements in fuel consumption and because of all the nice additives I get a much higher mileage which brings the total cost back to almost being competitive with running the 91. Also, the additives list in the 98 seems to keep my hi mileage landcrusier running more smoothly and better power (seat of the pants measurement on that last point).

There have been people who say their MPG improves, or goes back to where it was, once they switch back to the recommended octane level.
Personally I've never tried going to lower octane and then back to see if there really is an MPG difference.

In general:
Another thing to keep in mind is that timing control is not static, it's continuously variable based on sensor readings telling the ECU how the engine is performing.
Why is this important?
It's easily acceptable that an F30 driver using 89 isn't experiencing any performance problems because in order to continually pull timing the engine would have to continually knock at such a level such that the sensor would tell the ECU to keep correcting.

However, knock events that would trigger an adjustment may not be happening all that often even with 89US octane.
Knock tends to rear it's ugly head under heavy loads, such as driving up steep inclined roads on a hot day, or driving hard through twistys at higher rpm and the temps are hot. These conditions are when knock can come out to play.
If a driver is simply commuting at average speeds and at lower rpm, those knock events may simply not manifest.
The ECU continually strive to bring tuning up to optimal.
So if there aren't knock events even when using 89 there is no reason for the ECU to pull timing. The engine will be running at peak performance under those driving conditions.

In winter and colder temps the chances for knock events is lessened.
It's safer to run lower than optimal octane during this type of weather condition. So, I can see why some say their engine is running just fine and they feel no difference.
The problem of knock becomes more likely with drivers who like to drive harder more often where they are driving their engines at higher rpm and the engines running hotter. This type of driver may very well feel a decrease in performance when using lower octane fuel.
And in the summer months lower than optimal octane may really decrease performance as the hotter atmospheric temps combined with hard running higher loads and engine temps create a condition that calls knock out to play.

I choose to run higher octane year round not only because the engine was designed/tuned to use it, but also because it provides a greater cushion before the conditions become favorable for knock.
By using the correct octane the engine will always be running at it's highest state of tune instead of a continual state of correction and lower tuning level.

We, at least I, buy these cars for the performance they provide from these great engines. I want my engine to perform at it's highest level of tune and not at it's lowest level of acceptable before damage can occur.

[MarkyMarkOz]

Originally Posted by RPM90

In general:
Another thing to keep in mind is that timing control is not static, it's continuously variable based on sensor readings telling the ECU how the engine is performing.

Interesting point, because the times I have switched back and forth between fuels experimenting and measuring on the V8 Landcrusier, it 'seems' to take at least 2 tank fulls when switching back to the higher octane premium before the fuel consumption returns to it's optimum (i run it right down so there is minimal mix, plus with 135 litres the mix will be small). Almost like the car is tuning and learning again over at least 2 tank fills??

And agree with your last point emphatically. I dont see the point of having a luxury turbo car and not running good fuel in it, IMHO.

[rwrwrwrw]

See this article from FTC>
http://www.ftc.gov/bcp/edu/pubs/cons...tos/aut12.shtm

and this show was interesting too >>
http://www.cbc.ca/marketplace/episod...mpfiction.html

[BavarianFanatic]

This forum is like Groundhog Day all over again. How many times are the same subjects/arguments/discussions going to be recycled?

Unrelated - did you know the seat frames on the F30 come rusty from the factory and that it causes the brakes to squeal and the steering wheel to vibrate? True story.

[MarkyMarkOz]

Originally Posted by BavarianFanatic

This forum is like Groundhog Day all over again. How many times are the same subjects/arguments/discussions going to be recycled?

Unrelated - did you know the seat frames on the F30 come rusty from the factory and that it causes the brakes to squeal and the steering wheel to vibrate? True story.

For an old Hog it might be old, but us new Hogs to the forum it is new. Dont be too jaded in these public forums and become all seeing and knowing.

I like my rusty seats. They give at least 0.2 bar additional boost.

[HighlandPete]

NOTE: this post is using UK fuel ratings.

BMW used to say something like this in UK data:

The petrol engines are designed for RON 98 grade fuel. They can be run on fuel grades down to RON 91 with a decrease in power.

Sometimes adding:

and an increase in fuel consumption.

Current literature for the 3 and 5-series in the UK "recommends using RON 95", makes the comment on fuel grades down to RON 91 and then adds "Output and consumption figures apply to RON 98 fuel". But BMW have dropped the "designed for RON 98" comment.

For my engine N55 (535i) brochure and user manual "recommends the use of RON 95 super unleaded..." RON 95 is not "super" unleaded in the UK, RON 97/98 is super unleaded.

No wonder there is confusion in the different markets, if BMW don't seem to be consistent in their comments. Why test with the higher octane rated fuel, RON 98, and then recommend a lower octane, RON 95?

I think the clue is in the earlier comments, "output and consumption with the RON 98", or am I a cynic?

Go figure.

BTW, having tried different fuels, I now use a super unleaded fuel, RON97/98. Engine is smoother, quieter, butt dyno senses it is more eager in the mid range when pulling hard, and typically returns a better mpg.

HighlandPete

[redbullto]

In my part of the world, the oil companies charge 15 cents/litre more for 89 over 87 (or 50 cents US gallon). I therefore never bought it because it was merely 'recommended'. I never noticed any difference in performance in the e90. I just bought the new f30 with the 4cyl turbo and after reading this thread and against my better judgement I decided to splurge and bought 91. Guess what? No difference in performance or mileage. It's all bs. Save the cash and stick with 87.

[S-Dot]

Originally Posted by redbullto

In my part of the world, the oil companies charge 15 cents/litre more for 89 over 87 (or 50 cents US gallon). I therefore never bought it because it was merely 'recommended'. I never noticed any difference in performance in the e90. I just bought the new f30 with the 4cyl turbo and after reading this thread and against my better judgement I decided to splurge and bought 91. Guess what? No difference in performance or mileage. It's all bs. Save the cash and stick with 87.

There may be some microscopic cracks in your scientific method.

[///MZ]

Originally Posted by EB_F30

Less octane in the fuel is not going to burn as well...more octane equals more power because the fuel is more potent and it's also burning more air...thus making more power. I highly suggest not running 89 in a turbo car, you can lean the car out causing detention, especially in the high RPM's. It's very bad for the engine.

The quality of the burn is a common misconception. The speed of the burn is what is affected by the octane level. Your pistons reach top dead center when your cylinder pressure is at maximum, which is a function of your octane level.

Using 89 octane means it will burn quicker and therefore when your pistons are reaching TDC, you have already lost the optimal power generation point.

[sean10mm]

Originally Posted by rswbmw

See this article from FTC>
http://www.ftc.gov/bcp/edu/pubs/cons...tos/aut12.shtm

The first bullet point in the article is "READ YOUR OWNER'S MANUAL"

"Unless it’s recommended by your owner’s manual, don’t spend the money on high octane gas."

Notice the bolded part?

And what do all these BMW owner's manuals from around the world recommend under "Recommended Fuel Quality"? Higher-than-standard octane, with the numbers being pretty much the same when you adjust for the different measuring systems.

I mean, the FTC literally says , that's a pretty big hint.

[Elk]

Originally Posted by sean10mm

"READ YOUR OWNER'S MANUAL"

Amusingly, the 2013 manual states BMW recommends both: "BMW recommends AKI 89" and "BMW recommends AKI 91"

The 2012 manual makes no mention of AKI 91, only that AKI 89 is the recommended minimum octane.

Thus, use either 89 or 91, your choice. Pick one. Or both.

Don't agonize over the issue, it is a small question even in the world of cars - much smaller in any larger context.

[bnekic]

When I open my gas door it says use premium fuel which is 91 octane or higher. Why are people still talking about this?

USE PREMIUM GAS IN YOUR TURBOCHARGED BMW!!

[Elk]

^ See above.

We have already addressed your absolute, and wrong, claims.

[bnekic]

Originally Posted by Elk

^ See above.

We have already addressed your absolute, and wrong, claims.

Haha wow, pure ignorance.