[ExZHP]

I have been using premium all this time, but I recently noticed it says "89 min" on the door, so was wondering if that was acceptable and if there's any difference, for the engine and performance. Apologies if this has been threaded already.

[Gamb1t]

Down the rabbit hole we go again!

91 and 89 AKI.... the modern engines are able to cope with either. I'd pay attention to Top Tier fuel providers more.

Looking forward to your next post on what engine oil to use.

[ExZHP]

Pardon me if I had not gone down the previous rabbit hole!

And thanks.

[Rayscott]

Exxon Premium 91 grade here.

[Elvisfan]

You probably won’t get the best performance with the min.

[aerostar]

Originally Posted by ExZHP

I have been using premium all this time, but I recently noticed it says "89 min" on the door, so was wondering if that was acceptable and if there's any difference, for the engine and performance. Apologies if this has been threaded already.

You can get away with 89.

The computer will adjust timing to minimize knock. You should only go below 91 octane in an emergency. And don't ever WOT when you don't have 91 in the tank.

[happyjack]

shell v-power 93 whenever i can get it. have used it in every bimmer I’ve owned.

the price difference between that and mid-grade / 89 is onlylike $250 per year if you fill up once per week.

[ny176]

Always use Premium as well 93 octane

[RoundelM3]

Haven't put anything but 93 octane in all my BMWs since 2001. All BMWs have the same fuel requirement, and the "minimum 89" means you can't run "regular" gas, but 89 will be ok in an emergency situation when 91 or 93 isn't available. The difference in cost for a fill-up will be about what you pay for one of those mocha-choca-lava-java coffees at Starbucks.

[Maynard]

Top Tier gas is all I'd use, unless I was stuck w/o options (http://www.toptiergas.com/licensedbrands/). I think the car is smart enough that if you use lower octanes, all you get is less boost and lost performance, not detonation holes in pistons - presto! you save $3 a fillup and turn your BMW into a Toyota.

Reminds me I need to run another bottle of Techron through as well.

[Shovelman]

For my DD 89 is fine, though sometimes 91.

[ExZHP]

Originally Posted by aerostar

You can get away with 89.

The computer will adjust timing to minimize knock. You should only go below 91 octane in an emergency. And don't ever WOT when you don't have 91 in the tank.

WOT?

[pz619]

Originally Posted by ExZHP

WOT?

Wide Open Throttle, i.e. flooring it.

[harma24]

If the car says 89 required, 89 is just fine for everyday driving, even at WOT.

AAA has studied this. The efficiency and HP gains are minimal at best:

http://newsroom.aaa.com/wp-content/u...rt-FINAL-2.pdf

It's interesting to note that an A3, which is probably the closest car in the study to a 2-series, actually had reduced fuel economy with 91 octane vs. 89 octane.

[aerostar]

Originally Posted by harma24

If the car says 89 required, 89 is just fine for everyday driving, even at WOT.

AAA has studied this. The efficiency and HP gains are minimal at best:

http://newsroom.aaa.com/wp-content/u...rt-FINAL-2.pdf

It's interesting to note that an A3, which is probably the closest car in the study to a 2-series, actually had reduced fuel economy with 91 octane vs. 89 octane.

Um, clearly you didn't read the article you posted very well. MPG and max HP should not be used as a basis on what type of gasoline you use.

"During road testing, the Audi A3 had harsh audible engine knock in road driving using regular gasoline. In real-world driving, this audible knock is the primary decision making factor to select premium gasoline for this vehicle".

I would never drive a turbo vehicle hard without having proper fuel in it. Anything under 91 will develop engine knock and can cause SEVERE engine damage.

[Maynard]

This really has been beaten to death in several other threads. Those 'you don't need premium' stories are for the commuter cars, not something making >120hp/liter on turbo. And as noted by Aerostar, there are differences that are not trivial.

"During road testing, the Audi A3 had harsh audible engine knock in road driving using regular gasoline".

That audible 'knock' is not just annoying noise, it is putting tremendous unwanted stress on some VERY expensive internals. I'm actually disappointed that Audi allows enough of it to actually be audible - kind of scary (I thought they would just pull boost to prevent this). You probably won't throw a rod from it this weekend, but you will be one of those who wonders "why BMW can't make an engine that lasts more than 60-70k miles". And really, you bought a hi-po euro performance car and now you want to cheap out on a few dollars at the pump?

Edit: I waded through the whole report, actually some interesting stuff. You can see how the Audi had to pull boost on regular, vs. NA cars like Miata that show little variation. And almost universal increase in Hp/Tq and mileage w/ premium, just that it is not worth the extra $$.

[lateapex'er]

Shell 93

[aerostar]

Originally Posted by Maynard

This really has been beaten to death in several other threads. Those 'you don't need premium' stories are for the commuter cars, not something making >120hp/liter on turbo. And as noted by Aerostar, there are differences that are not trivial.

"During road testing, the Audi A3 had harsh audible engine knock in road driving using regular gasoline".

That audible 'knock' is not just annoying noise, it is putting tremendous unwanted stress on some VERY expensive internals. I'm actually disappointed that Audi allows enough of it to actually be audible - kind of scary (I thought they would just pull boost to prevent this). You probably won't throw a rod from it this weekend, but you will be one of those who wonders "why BMW can't make an engine that lasts more than 60-70k miles". And really, you bought a hi-po euro performance car and now you want to cheap out on a few dollars at the pump?

Edit: I waded through the whole report, actually some interesting stuff. You can see how the Audi had to pull boost on regular, vs. NA cars like Miata that show little variation. And almost universal increase in Hp/Tq and mileage w/ premium, just that it is not worth the extra $$.

It's also worth nothing that higher octane fuel burns cleaner, leaving less residual deposits in the motor.

The amount of additional maintenance you'll be doing by saving a few cents using lower octane fuel will vastly outweigh just paying for the 91+ octane.

[harma24]

Originally Posted by aerostar

I would never drive a turbo vehicle hard without having proper fuel in it. Anything under 91 will develop engine knock and can cause SEVERE engine damage.

They were running it with 87 octane. Although this is the minimum rating for the A3, that would appear to have been a mistake. Our cars require 89 octane minimum. Have you ever run with 89 octane in your car? Plenty of people on this forum have. With 89 octane, there's no knock, even at WOT.

For the record, I use 93 the majority of the time, but will use 89 occasionally. One time at a full service station, I found that the attendant filled the car with 87. I think this has happened to others on this forum as well. I drove gingerly and did not have any trouble; I did not try WOT with 87 in the tank.

[aerostar]

Originally Posted by harma24

They were running it with 87 octane. Although this is the minimum rating for the A3, that would appear to have been a mistake. Our cars require 89 octane minimum. Have you ever run with 89 octane in your car? Plenty of people on this forum have. With 89 octane, there's no knock, even at WOT.

For the record, I use 93 the majority of the time, but will use 89 occasionally. One time at a full service station, I found that the attendant filled the car with 87. I think this has happened to others on this forum as well. I drove gingerly and did not have any trouble; I did not try WOT with 87 in the tank.

The manually literally states that BMW recommends you to run 91 octane and that 89 is a minimum. Maybe 89 is the minimum for no knock but probably not the best for the motor in general.

If you feel there's no difference why are you running 93?

[harma24]

Originally Posted by aerostar

The manually literally states that BMW recommends you to run 91 octane and that 89 is a minimum. Maybe 89 is the minimum for no knock but probably not the best for the motor in general.

If you feel there's no difference why are you running 93?

I never said there is no difference between the two octanes. There IS a difference, and the difference in performance is documented in the study.

However, the difference in HP is minimal, and as documented in the study, the difference in fuel economy is not enough to cover the higher cost of 93 vs. 87 (I have not done the math to see if the increased gas mileage is enough to justify the difference between 89 & 93).

89 is the minimum for no knock per BMW. That means that in the opinion of BMW engineers the engine is capable of adjusting the timing sufficiently to run on 89 with no risk of damage to the engine. They would not say 89 minimum if it were a risk. Otherwise, they would be opening themselves up to all sorts of warranty claims and potentially lawsuits.


So, after all that, why do I run 93 personally? For one, habit. My last car required 91 octane (it did not recommend anything above that, just a minimum). Since I can't get 91 around here, I bought 93. Second, even if the performance gain is minimal (let's just say 1.5% for the sake of argument), I want that 5 extra horsepower! To heck with the extra cost; if I was concerned with saving a few bucks on gas, I'd be driving around in Eco mode!

[mike@x-ph.com]

93 if available, if not 91