What fuel grade do you use?
09-06-2005, 10:30 AM
#21
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Shell V Power... 91 Octane. IMHO it is truly to very best! 
09-06-2005, 11:19 AM
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I mix 93 and 89 50/50 to get....voila....91 octane. The 645 calls for 91 octane.
Why use anything higher with a stock engine? It costs more and you are hurting your performance and economy.
Why use anything higher with a stock engine? It costs more and you are hurting your performance and economy.
09-06-2005, 03:33 PM
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Originally Posted by PKandCK' date='Sep 6 2005, 08:30 PM
Shell V Power... 91 Octane.? IMHO it is truly to very best!
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In Germany the Shell V-Power is 100 octane - and that's the ONLY stuff I use!
09-06-2005, 03:47 PM
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Shell V Power 93 octane IMO the best
cheers
vern
cheers
vern
09-07-2005, 04:20 AM
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It costs more and you are hurting your performance and economy.
The octane rating is a measure of how resistant the fuel is to igniting from the increased pressures created inside the engine. A high compression engine, like one in a BMW, requires that the fuel withstand higher pressures than a typical car. That's why we need to use high octane gas.
09-07-2005, 12:01 PM
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You contradict yourself. This is ricer Honda "wing adds 40 hp" type thinking.
Using too high an octane rating hurts performance. Period.
Octane is a measure of resistance to burning/detonating.
If the fuel/air wants to keep from exploding but the computer expects it to explode at a given point, guess what happens? Octane ratings are a roundabout measure of explosion resistance, right?
Too low of an octane rating produces knock. Yes. But try running 110 unleaded in your car and see what happens to your powerband.
Extra octane numbers aren't "good" or "performance oriented" by themselves. They require an engine that has a high DCR at a given time, whether that be through N20, forced induction or high compression.
You need to use the proper octane fuel for the specific application. Period.
I know big-block Chevy egnines that make 700 hp and run on 87 octane fuel in street trim. Change the cam and maybe you'll need more octane, but that's a different application, now isn;t it?
If the 3.0 L engine calls for 91 and you're putting in 93, the only benefit you get is between your ears. The rest goes to the oil companies. The only possible benefit I can see is if you're running in an extrememly hot environment and the computer pulls timing on 91 because it's so hot that knock is occurring. You'd have to be in the Mojave desert at the summer solstice at 2:30 pm for this to happen, as I'm sure BMW factors into their programming summertime driving on the blacktop highway in stop and go traffic
I realize that the Euro rating is different from the US rating, but this has nothing to do with the fact that you're wasting money and hurting performance if you're running anything higher than 91 octane in a STOCK 3.0L engine. No chip upgrades, no blower, no nitrous, so on and so forth. In a stock application you are wasting money and hurting performance, period.
Using too high an octane rating hurts performance. Period.
Octane is a measure of resistance to burning/detonating.
If the fuel/air wants to keep from exploding but the computer expects it to explode at a given point, guess what happens? Octane ratings are a roundabout measure of explosion resistance, right?
Too low of an octane rating produces knock. Yes. But try running 110 unleaded in your car and see what happens to your powerband.
Extra octane numbers aren't "good" or "performance oriented" by themselves. They require an engine that has a high DCR at a given time, whether that be through N20, forced induction or high compression.
You need to use the proper octane fuel for the specific application. Period.
I know big-block Chevy egnines that make 700 hp and run on 87 octane fuel in street trim. Change the cam and maybe you'll need more octane, but that's a different application, now isn;t it?
If the 3.0 L engine calls for 91 and you're putting in 93, the only benefit you get is between your ears. The rest goes to the oil companies. The only possible benefit I can see is if you're running in an extrememly hot environment and the computer pulls timing on 91 because it's so hot that knock is occurring. You'd have to be in the Mojave desert at the summer solstice at 2:30 pm for this to happen, as I'm sure BMW factors into their programming summertime driving on the blacktop highway in stop and go traffic
I realize that the Euro rating is different from the US rating, but this has nothing to do with the fact that you're wasting money and hurting performance if you're running anything higher than 91 octane in a STOCK 3.0L engine. No chip upgrades, no blower, no nitrous, so on and so forth. In a stock application you are wasting money and hurting performance, period.
09-07-2005, 12:50 PM
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Originally Posted by TB CD' date='Sep 7 2005, 03:01 PM
You contradict yourself.? This is ricer Honda "wing adds 40 hp" type thinking.
Using too high an octane rating hurts performance.? Period.
Octane is a measure of resistance to burning/detonating.
If the fuel/air wants to keep from exploding but the computer expects it to explode at a given point, guess what happens?? Octane ratings are a roundabout measure of explosion resistance, right?
Too low of an octane rating produces knock.? Yes.? But try running 110 unleaded in your car and see what happens to your powerband.
Extra octane numbers aren't "good" or "performance oriented" by themselves.? They require an engine that has a high DCR at a given time, whether that be through N20, forced induction or high compression.
You need to use the proper octane fuel for the specific application.? Period.
I know big-block Chevy egnines that make 700 hp and run on 87 octane fuel in street trim.? Change the cam and maybe you'll need more octane, but that's a different application, now isn;t it?
If the 3.0 L engine calls for 91 and you're putting in 93, the only benefit you get is between your ears.? The rest goes to the oil companies.? The only possible benefit I can see is if you're running in an extrememly hot environment and the computer pulls timing on 91 because it's so hot that knock is occurring.? You'd have to be in the Mojave desert at the summer solstice at 2:30 pm for this to happen, as I'm sure BMW factors into their programming? summertime driving on the blacktop highway in stop and go traffic
I realize that the Euro rating is different from the US rating, but this has nothing to do with the fact that you're wasting money and hurting performance if you're running anything higher than 91 octane in a STOCK 3.0L engine.? No chip upgrades, no blower, no nitrous, so on and so forth.? In a stock application you are wasting money and hurting performance, period.
Using too high an octane rating hurts performance.? Period.
Octane is a measure of resistance to burning/detonating.
If the fuel/air wants to keep from exploding but the computer expects it to explode at a given point, guess what happens?? Octane ratings are a roundabout measure of explosion resistance, right?
Too low of an octane rating produces knock.? Yes.? But try running 110 unleaded in your car and see what happens to your powerband.
Extra octane numbers aren't "good" or "performance oriented" by themselves.? They require an engine that has a high DCR at a given time, whether that be through N20, forced induction or high compression.
You need to use the proper octane fuel for the specific application.? Period.
I know big-block Chevy egnines that make 700 hp and run on 87 octane fuel in street trim.? Change the cam and maybe you'll need more octane, but that's a different application, now isn;t it?
If the 3.0 L engine calls for 91 and you're putting in 93, the only benefit you get is between your ears.? The rest goes to the oil companies.? The only possible benefit I can see is if you're running in an extrememly hot environment and the computer pulls timing on 91 because it's so hot that knock is occurring.? You'd have to be in the Mojave desert at the summer solstice at 2:30 pm for this to happen, as I'm sure BMW factors into their programming? summertime driving on the blacktop highway in stop and go traffic
I realize that the Euro rating is different from the US rating, but this has nothing to do with the fact that you're wasting money and hurting performance if you're running anything higher than 91 octane in a STOCK 3.0L engine.? No chip upgrades, no blower, no nitrous, so on and so forth.? In a stock application you are wasting money and hurting performance, period.
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I think we're vastly oversimplifying several complex sets of metrics, and even misstating a few.
Octane is a metric that is used to measure a gasoline's resistance to premature detonation (knocking).
RON is a metric that is used to measure octane as well.
More on octane:
http://en.wikipedia.org/wiki/Octane_rating
Interestingly, it would appear that 91 octane based on the AKI metric (US) would be about 96 in EU.
The amount of energy content present in a fuel is represented by BTU.
For what it's worth, the toptiergas.com fuels -must- contain at least 8% ethanol but less than 10% by volume. Once it hits 10% it's officially "gasohol". The BTUs for gasoline vs. 10% ethanol blends is:
gasoline - 104,000 BTU/US Gal
gasohol - 100,700 BTU/US Gal
Regardless of octane, the BTU is the final measure of energy that the fuel contains. We know that for toptiergas vendors it's something more than 100,700 and less than the 104,000 BTUs in pure gasoline.
This tutorial is enlightening:
http://en.wikipedia.org/wiki/Gasoline
The FTC has something to say about high octane gas as well:
http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm
It won't help you, but I'd argue it won't hurt you either when we're dealing with such small increases. Computers are smart and engine management has come a long way in the decades since its inception. Most US states don't even have 91 available - I guess it's a ploy to get you to buy 92 or 93.
09-07-2005, 02:17 PM
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Originally Posted by UUronL' date='Sep 7 2005, 10:50 PM
...It won't help you, ...
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There are two groups of people, the ones that believe it helps, the other ones that believe it doesn't help...
Unless it is proven that it doesn't make ANY difference, I get the 100 octane (EU).
