[MichaelL]

91 in CA

[ABPReader]

Shell VPower 100 in Switzerland, it should be equal to 94 in the US

[msej449]

I use shell V-Power Nitro+ 97 or BP Ultimate 97 here in the UK, mainly because of the additives rather than performance/MPG. For my M235i, filling-up with a bit still in the tank (say 50 litres or about 13.2 US Gallons) costs US $73, compared to $63 for the cheapest, plain supermarket 95 (=US 91) with no additives. As others have opined, a $10 a fill-up premium for a car I'm likely to keep for a while, and which cost me around $48K is part of the overall cost of ownership.

[DMB228]

Originally Posted by wjones14

91 octane is hard to come by in southeastern CT as well, but not impossible. Sunoco stations have 87, 89, 91, and 93. I always use Sunoco 91.

Yup live in CT as well and it's hard to find 91 as noted above so I use 89 per the manual. I have also read a lot about gas grades and what they mean and agree 93 is a waste of money for my 228i. I was excited to learn before I purchased this car that it didn't require premium

[Maynard]

Originally Posted by wjones14

Not saying you're wrong, but can you provide a link?

Indirect, but to me compelling, is the logical argument. These motors make huge torque, limited at lower rpm by the knock sensor - if they weren't holding back at low rpm then you would see a typical shape to the torque curve, not the 'table-top'. Letting them run up to the knock limit will get more out of them at realistic street rpms. Check out the dyno data for the stock N20 here (http://www.2addicts.com/forums/showthread.php?t=1282053) on 93 octane 263/286, vs advertised 240/260. Don't think it is accidental that all the tuners recc at least 93 octane (but would be neat to see dynos just comparing that in a stock motor).

Adding to this, and really the key for me, is damage control. The knock sensors limit, but can't stop those first few hits, more common with the lower octane. Best description I've heard of knock is that it is like hitting the piston off-center with a machete (flame front), and driving the skirt into the wall - often this force will shear thru the oil barrier into metal to metal contact (and on bearing surfaces). Much of the reason why those stop-go and cold starts are 90% of engine wear is this metal-metal contact. I figure that the extra cost would be eaten up by even one trip to the dealership, especially since this is the stuff that crops up late, out of warranty. I suspect this is why you don't see tuners trying to put out low-octane setups - it isn't worth the risk of an engine over a few bucks in gas.

[Viffermike]

I'm in North Texas, where the typical jump is from 89 to 93 -- 91 isn't very common. On top of that, our fuels -- even Top Tier ones -- frequently contain 10 percent ethanol because of federal smog guidelines.

For that reason I don't even look at 89. 93 all the way.

Edit: I realize that ethanol natively has a higher octane than refined gasoline. I would just rather pay a little more and 'play it safe' -- and I swear that I can tell a difference between how my N20 runs on 89 vs. 93.

[harma24]

Originally Posted by Maynard

I suspect this is why you don't see tuners trying to put out low-octane setups - it isn't worth the risk of an engine over a few bucks in gas.

Tuning is different. They are pushing the engine harder than the factory intended. Higher pressures increase the risk of knocking, and would thereby justify a higher octane.

I'm looking for feedback on stock engines.

[Merc for hire]

I put 89 in my M235i. I don't get to use the full power often in city driving. The car is going back to dealer in 2 years anyway.

[kdog26372]

I thought a tuner ran dyno comparison of M2 with 91 and 93 and it made a good amount more power on the 93. Of course that's essentially a tuned m235i, but I surely wouldn't run 89 octane and only 91 if there were no better options. I have tune and run 2 gallons E85 and rest is 93 octane. Runs great.

[bimmerfile]

Shell V-Power® NiTRO+ Premium Gasoline

[ORIGIN M.]

Damn Canadians... !

Originally Posted by Dylan86

94 only.

[amw896]

87 from the local 7-11 baby! Now that I think of it, I have been getting weird engine behaviour. Oh well, that's what leasing is for.

[pz619]

Originally Posted by amw896

87 from the local 7-11 baby! Now that I think of it, I have been getting weird engine behaviour. Oh well, that's what leasing is for.

Well... citgo is technically top tier rated.

[3.0L]

I use 91 octane exclusively here in California.

[Sypher]

91 ethanol free. Petro Canada's 94 here is an ethanol blend

[VIDoug]

Most fill ups I pump Chevron - 94 octane with no ethanol

[siwo]

I fuel 93 from Esso. I contemplated going 91 a while but since I go to Esso here in Toronto as my main source, I wasn't sure if their 91 is up to it so I chose 93.

[RoundelM3]

Never have used anything less than 93 in any of my BMWs or (previously) Porsches. There are a few stations in the area that have ethanol-free 93, which is the better fuel, but they're not very close by.

[Dylan86]

Originally Posted by VIDoug

Most fill ups I pump Chevron - 94 octane with no ethanol

Chevron all the way!

Originally Posted by red-sauerkraut

Damn Canadians... !

That $1.40/L though

[AlpsRider]

CA 91, + 2 gallons of 100 octane = $$$

[wjones14]

Originally Posted by Maynard

Adding to this, and really the key for me, is damage control. The knock sensors limit, but can't stop those first few hits, more common with the lower octane.

Well again, the manual says that 89 is the minimum, and 91 octane is recommended. So I can't see how 91 is going to cause engine damage. If so, why wouldn't BMW recommend 93?

I use 91, because I will go with the manufacturer's recommendation.

I ran CITGO 87 octane in my 4.6 liter 2005 Mustang GT for 10 years and that car ran stronger when I sold it than it ever did. The manual recommended 87.

My daughter bought a 5 year old 2003 Mini in 2008, but before buying the car my wife was concerned that the manual said the recommended octane was 91. My daughter was going to college at the time, and the wife just didn't want any unnecessary expenses. So we emailed Mini corporate and got back a very nice reply saying that 91 is recommended for maximum efficiency and performance, but 87 would not hurt the engine. So most of the time my daughter put 87 in it. I bought the car from her 3 years ago and have put 91 octane in it since, and the car has 101,000 miles now and there are no engine problems whatsoever.

[XutvJet]

In Kansas City, the only store that sells 93 is BP and that's all I've run the car since buying it back in Feb of this year. Last night I bought Shell 91 as an experiment because so many BMW owners swear it's the best fuel. My experiment is to gauge MPGs and overall driveability. I'll report back once I use up that tank.

Octane is a fuel's resistant to burn and pre-detonate. In a high compression turbo more, a lot of heat is generated and the possibility for pre-detonation is much high thus the need for higher octane fuel. The DME in late model BMW cars is very smart and quick to react. if the DME senses detonation, it will reduce timing, add fuel, etc. (reduce power) to stop this dangerous situation. Running greater than 91 octane should not technically make more power, but it can allow the motor to run at it's peak power and delivery more consistant power.