[SROC3]

The recommended Octane for our cars (US side) is 91 octane (or 93). There is a gas station near my house that sells 102 octane gas. Is it a bad idea to put it in or will the ECU automatically adjust to this fuel type? The last thing I want is the engine running too lean and detonating.

[Mr. Smith]

i am not sure about you question but i have my own:

Do you have to use 91 octane or higher, can you use Mid-Grade gas? or even Low-Grade?

[bobnaz]

Originally Posted by Mr. Smith

i am not sure about you question but i have my own:

Do you have to use 91 octane or higher, can you use Mid-Grade gas? or even Low-Grade?

91 or better. I think you can even use 89 according to the manual. You could spend more$$, but I don't think you will notice any difference. IMHO.

[///Matt]

if you use anything below 91 your DME (digital motor electronics) will retard your timing to avoid knock, and you will lose a LOT of HP. VERY noticable loss.

102 will make your car run better, faster, and get better mileage, except you'll have your foot in it all the time, so your mileage will go DOWN. lol.

The problem with 102 is that it will wear out your Catalytic Converters more quickly. How much more quickly? can't say. but it will.

[///Matt]

Forgot to mention... you probably won't notice ANYTHING on your first tank of 102, unless you reset all the fuel trim adaptations at the dealer. Otherwise, it will take a couple tanks for the car to figure out it's a badass. =)_

[wj4]

on stock ECU, that high of an octane wouldn't do much good for the car.
A lot of my friends use c16 or 100+ octane gas when racing to go with race maps on their ECU. This helps shorten the 1/4 mile time down a bit, but since you are stock, it won't do much good.
And let me take a guess, is this gas station happen to be a 76 by anychance? lol.

[Mr. Smith]

so mid-grade is okay, and low-grade is a definent no-no

[///Matt]

anything under 91 is a no no. don't do that to your BMW bud. it's not a toyota.

Also... wj4....

You're wrong. I'm sorry to say, but you're wrong. I've tried high octane gas. It's a real benefit. i mean REAL. like about 20 hp real. I'm not kidding, or making it up. Again, I'm talking about putting high octane in and then resetting the DME adaptations, not just putting it in and driving.

[mistersamu]

in spain octane is 98 jejej no problem

[jxsanche]

Originally Posted by SROC3

The recommended Octane for our cars (US side) is 91 octane (or 93). There is a gas station near my house that sells 102 octane gas. Is it a bad idea to put it in or will the ECU automatically adjust to this fuel type? The last thing I want is the engine running too lean and detonating.

I find this link rather interesting:
http://www.cars.com/carsapp/national...odaysgas1.tmpl

[wj4]

Originally Posted by ///Matt

anything under 91 is a no no. don't do that to your BMW bud. it's not a toyota.

Also... wj4....

You're wrong. I'm sorry to say, but you're wrong. I've tried high octane gas. It's a real benefit. i mean REAL. like about 20 hp real. I'm not kidding, or making it up. Again, I'm talking about putting high octane in and then resetting the DME adaptations, not just putting it in and driving.

I've put 100 octane in my car when it was stock and dyno'd it. It was a little bit more than 91 octane. There's a little gain, but my butt can not feel much of a different when I drove it. The last time I dyno'd my car, I dyno'd at 300whp on 91 octane, and I put in some 100 octane just for the hell of it, and it yields about 330whp. I too would like to think that the 100 made my car faster as it is pricey per gallon.
100 octane isn't worth it if your car isn't prepped for it IMO. Just look at Shiv's post about his tuning in Canada where they have 94 octane, and compared his dyno result to his own car with Cali's inferior 91 octane.

There's a reason why they sell high octane gas at LACR and other race tracks

[13307]

Unfortunately in this car, you will not gain any measurable HP with the higher octane. Believe me I wish this were true, but 20 years of racing everything from shifter karts, motocross, superbikes, to scca formula ford events has shown that the stock ECU's will not compensate for higher octane, the sensors(used to be knock, now are straight up timing) are unilateral, the ECU does not have the programming to detect higher octane and therefore compensate, bear in mind that the ECU does not have the parameters to advance the timing beyond factory only retard. Now that being said, if you look at any race vehicle(2 or 4 stroke), no one uses factory ignitions(for older low tech engines) or ECU's. I just recently went through this on a 5 valve yamaha engine in which I increased compression throughout the range, ported and polished the heads, and reprogrammed the ECU, all of this then requires me to run VP110 fuel, if gains could have been made with simply running higher octane without modifications, every R1 out there would do it. Again, once you start tweaking the engine, you benefit from the higher octane(although more accurately you require it), but I defy anyone to show increased wheel horsepower with simply increases the octane and nothing else. Of course you could have Shiv chime in and talk about how he tuned the 335's and see what he did with required fuel, but I am betting he'll say the same thing, he'll give you the best performance based on what fuel you say you're willing to run, not the other way around. If you speak with Dinan as well, they used to do custom programming for the old M3's for GT events and you would tell them what the spec fuel was for the class or specific event and they would tune the car for that. Now, one concession I will make is with regard to the recent ongoing reports of fuel coming in sub-spec on octane levels at the pump, and if you are buying 91 and only getting 89/89.5, and then you run a race gas, you will feel the horsepower, not because the extra 8 points of octane are benefitting you, but because you were not getting the minimum required to begin with. I'm in SE PA, and I stock GT100 gas for one motorcycle and one shifter kart, as well as VP110 for a moto, if anyone is interested in trying it on the dyno. I said if anyone is interested, because without witnesses, the forum will light up with people disputing the results! Best of Luck.

[Jaws]

Originally Posted by mistersamu

in spain octane is 98 jejej no problem

Different scales. Europe use RON, NA uses AKI.

[Jaws]

Originally Posted by 13307

Unfortunately in this car, you will not gain any measurable HP with the higher octane. Believe me I wish this were true, but 20 years of racing everything from shifter karts, motocross, superbikes, to scca formula ford events has shown that the stock ECU's will not compensate for higher octane, the sensors(used to be knock, now are straight up timing) are unilateral, the ECU does not have the programming to detect higher octane and therefore compensate, bear in mind that the ECU does not have the parameters to advance the timing beyond factory only retard. Now that being said, if you look at any race vehicle(2 or 4 stroke), no one uses factory ignitions(for older low tech engines) or ECU's. I just recently went through this on a 5 valve yamaha engine in which I increased compression throughout the range, ported and polished the heads, and reprogrammed the ECU, all of this then requires me to run VP110 fuel, if gains could have been made with simply running higher octane without modifications, every R1 out there would do it. Again, once you start tweaking the engine, you benefit from the higher octane(although more accurately you require it), but I defy anyone to show increased wheel horsepower with simply increases the octane and nothing else. Of course you could have Shiv chime in and talk about how he tuned the 335's and see what he did with required fuel, but I am betting he'll say the same thing, he'll give you the best performance based on what fuel you say you're willing to run, not the other way around. If you speak with Dinan as well, they used to do custom programming for the old M3's for GT events and you would tell them what the spec fuel was for the class or specific event and they would tune the car for that. Now, one concession I will make is with regard to the recent ongoing reports of fuel coming in sub-spec on octane levels at the pump, and if you are buying 91 and only getting 89/89.5, and then you run a race gas, you will feel the horsepower, not because the extra 8 points of octane are benefitting you, but because you were not getting the minimum required to begin with. I'm in SE PA, and I stock GT100 gas for one motorcycle and one shifter kart, as well as VP110 for a moto, if anyone is interested in trying it on the dyno. I said if anyone is interested, because without witnesses, the forum will light up with people disputing the results! Best of Luck.

Bang on. To summarize: Using higher octane than what the vehicle was designed for is a waste of money. You can only get more power with advanced timing and the PME has no way to advance the timing only to retard the timing through knock sensor inputs.

[martieg]

From HowStuffWorks.com - http://auto.howstuffworks.com/question90.htm

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

According to this, the only way to get a benefit is to increase compression ratio. Maybe that's what Matt is referring to. Without any mods or adjustments, you won't get anything from the more expensive gas.

Other cool links -

How turbochargers work - http://auto.howstuffworks.com/turbo.htm

How to increase the HP of your car - http://auto.howstuffworks.com/question395.htm

[SROC3]

Glacias......glacias everyone.....mucho greato informacion!!!!!! Thanks so much!

[Convertible]

Here in Europe BMW manuals say that BMW engines are made for 98 octane fuel (ron) if you use 95E usually the lowest oct. we got, then you'll experience power loss and higher fuel consumption.

There was a test in a Swedish magazine(Teknikes Värld) between BMW 130 (claimed 265hp) and a Audi A3 Sportback 3.2 quattro (claimed 250hp). They also tetsted the cars with different fuels. The Audi was brought to the test with 95E in the tank while BMW had 99E in the tank.

Well the Audi gave 219hp with 95E with 98E 248hp.
BMW 265hp with 98E and 272hp with 99E.


Here,s some result's from the test.

Audi BMW
0-50 km/h 2,55 2,53
0-100km/h 6,54 6,40
0-200km/h 29,14 22,46
402m 14,76 14,39
402m 154,80 163,68 km/h

[SoYank]

Originally Posted by SROC3

The recommended Octane for our cars (US side) is 91 octane (or 93). There is a gas station near my house that sells 102 octane gas. Is it a bad idea to put it in or will the ECU automatically adjust to this fuel type? The last thing I want is the engine running too lean and detonating.

Originally Posted by jxsanche

I find this link rather interesting:
http://www.cars.com/carsapp/national...odaysgas1.tmpl

So if Iso-octane has a 100 octane rating and heptane has 0 octane and gasoline is a mixture of both, how do you get an octane rating above 100?

[bobnaz]

Originally Posted by wj4

I've put 100 octane in my car when it was stock and dyno'd it. It was a little bit more than 91 octane. There's a little gain, but my butt can not feel much of a different when I drove it. The last time I dyno'd my car, I dyno'd at 300whp on 91 octane, and I put in some 100 octane just for the hell of it, and it yields about 330whp. I too would like to think that the 100 made my car faster as it is pricey per gallon.
100 octane isn't worth it if your car isn't prepped for it IMO. Just look at Shiv's post about his tuning in Canada where they have 94 octane, and compared his dyno result to his own car with Cali's inferior 91 octane.

There's a reason why they sell high octane gas at LACR and other race tracks

The higher octane sold at tracks are for modified engines that need the higher octane for a slower burn, still think it's a waste of $$ for street cars IMHO. Most guys I race with that have E36 M3's with a few high end mods mix75-90% 91 and 10-25% 101. I believe that Canadian and US autos are programed differentely

[RGB]

In Spain I'm using 95 octane -BMW reccomends here 95 to 98- and the car runs
ok. I'm going to do a few 98 fill ups and see if I can feel any difference.

[ksfrogman]

Originally Posted by ///Matt

anything under 91 is a no no. don't do that to your BMW bud. it's not a toyota.

Also... wj4....

You're wrong. I'm sorry to say, but you're wrong. I've tried high octane gas. It's a real benefit. i mean REAL. like about 20 hp real. I'm not kidding, or making it up. Again, I'm talking about putting high octane in and then resetting the DME adaptations, not just putting it in and driving.

Aha! Lol. I figured

[carl_d]

+1 Totally agree ... spot on.

Originally Posted by ///Matt

anything under 91 is a no no. don't do that to your BMW bud. it's not a toyota.

Also... wj4....

You're wrong. I'm sorry to say, but you're wrong. I've tried high octane gas. It's a real benefit. i mean REAL. like about 20 hp real. I'm not kidding, or making it up. Again, I'm talking about putting high octane in and then resetting the DME adaptations, not just putting it in and driving.