Do I need the expensive gas???

"dugies25" <UseLinkToEmail RemoveThis @AutoForumz.com> wrote in message
news:1_513265_0c6dd3587a443755212f0dcb0d3eb8f7@autoforumz.com...
 > I am pretty new to this "Ultimate Diving Machine" experience. I want
 > to treat my car right, but I also don't want to throw money out the
 > window when I don't need to. My previous cars have never required
 > premium gasoline, but they have never been BMW's either. I read in the
 > manul to use 91 octane or above to avoid knocking in the engine.

The manual says 91 or higher. Use 91 or higher. If the manual is
incorrect, you have legal recourse. If you cause damage by using the wrong
octane you're on your own.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

"dugies25" <UseLinkToEmail.RemoveThis@AutoForumz.com> wrote in message
news:1_513265_0c6dd3587a443755212f0dcb0d3eb8f7@autoforumz.com...
 > I am pretty new to this "Ultimate Diving Machine" experience. I want
 > to treat my car right, but I also don't want to throw money out the
 > window when I don't need to. My previous cars have never required
 > premium gasoline, but they have never been BMW's either. I read in the
 > manul to use 91 octane or above to avoid knocking in the engine. But I
 > have also heard reports that unless you are driving a super high
 > performance vehicle that your car won't know the difference between
 > 87, 89, or 93 octance gasoline. I have a 2003 330 CI, It is the most
 > high performance vehicle i have ever owned, but i don't know if it
 > qualifies as needing the higher octane gas...and with the gas prices
 > today, if it doesn't need it, I could save $5-$10 a week by getting
 > the lower gas. What does everyone think? Has anyone had experience
 > with knocking in their engine from lower octane gas?

You should use 91. You are right, you don't know if it qualifies as needing
the higher octane gas. However, luckily for you, BMW does know. They say
use 91. If you use lower grades, your car's anti-ping sensors will reduce
your engine's performance until the pinging stops, and you will enjoy
reduced performance from your machine. Why somebody would spend $30k or
$40k on a car and then reduce its performance to save $10 a week, I have no
idea.

What the article was *actually* telling you that if you use an octane level
in excess of that which is specified, there is no benefit. This is true.
93 octane will not get your car anything extra. 91 octane will not get my
car anything extra, because 89 is specified.

You can put a performance chip in your car, or many other cars. Such a chip
will modify the engine operating parameters to use the increased anti-ping
capabilities of higher rated gas. In that case, you must use the rating
indicated by the Chip manufacturer. In your case, a chip might require 93
octane, and to use less would impair performance. Which would negate the
reaons for buying the chip in the first place.

-Russ.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

"Troika" <lank.RemoveThis@sympatico.ca> wrote in message
news:aUX1e.625$x8.266936@news20.bellglobal.com...
 > 91 or 93 octane you now drive a car not only a better vehicle but in
order
 > to get better gas mileage
 > and performance and most of all stay away from the shop "dugies25"

I don't belive that he will get any better mileage, nor fewer repairs, by
using the correct grade of gas rather than an under-spec rating suchh as 89.
Do you have evidence to the contrary? The only problem will be reduced
performance.

-Russ.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

"Somebody" <somebody DeleteThis @nospam.russdoucet.com> wrote
 > "Troika" <lank DeleteThis @sympatico.ca> wrote
  >> 91 or 93 octane you now drive a car not only a better vehicle but in
 > order
  >> to get better gas mileage
  >> and performance and most of all stay away from the shop "dugies25"
 >
 > I don't belive that he will get any better mileage, nor fewer repairs, by
 > using the correct grade of gas rather than an under-spec rating suchh as
 > 89.
 > Do you have evidence to the contrary? The only problem will be reduced
 > performance.

Wrong. He will also get less mileage, because the engine computer
will have to run the engine richer to keep the intake charge cool.
Retarded ignition timing will also result in less mileage, in addition
to lower performance.

Floyd<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

dugies25 wrote:
 > I am pretty new to this "Ultimate Diving Machine" experience. I want
 > to treat my car right, but I also don’t want to throw money out the
 > window when I don’t need to. My previous cars have never required
 > premium gasoline, but they have never been BMW’s either. I read in the
 > manul to use 91 octane or above to avoid knocking in the engine. But I
 > have also heard reports that unless you are driving a super high
 > performance vehicle that your car won’t know the difference between
 > 87, 89, or 93 octance gasoline. I have a 2003 330 CI, It is the most
 > high performance vehicle i have ever owned, but i don’t know if it
 > qualifies as needing the higher octane gas...and with the gas prices
 > today, if it doesn’t need it, I could save $5-$10 a week by getting
 > the lower gas. What does everyone think? Has anyone had experience
 > with knocking in their engine from lower octane gas?
 >

The owner's manual says:
Fuel specifications
The engine uses lead-free gasoline only.
Required fuel:
Premium Unleaded Gasoline,
min. 91 AKI.
AKI = Anti Knock Index

So the answer is YES, you need to use premium fuel of at least 91 pump
octane in the US. If you use less you will get worse fuel economy and
run the risk of causing engine damage due to detonation (pinging).

At most stations the added cost of 10 cents per gallon is only about 5%
of the cost of the fuel (at ~ $2.00 per gallon). Hardly worth breaking
into a sweat about, is it?

-Fred W<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

Somebody wrote:
 > "Troika" <lank RemoveThis @sympatico.ca> wrote in message
 > news:aUX1e.625$x8.266936@news20.bellglobal.com...
 >
  >>91 or 93 octane you now drive a car not only a better vehicle but in
 >
 > order
 >
  >>to get better gas mileage
  >>and performance and most of all stay away from the shop "dugies25"
 >
 >
 > I don't belive that he will get any better mileage, nor fewer repairs, by
 > using the correct grade of gas rather than an under-spec rating suchh as 89.
 > Do you have evidence to the contrary? The only problem will be reduced
 > performance.

Russ,

Yes, actually, part of that reduced performance that you mention will be
reduced gas mileage. By retarding the spark you will no longer be
optimizing the combustion cycle to extract the most power per potential
BTU of energy in the gasoline. The potential power in both grades are
(roughly) the same, it's the reduced tuning that causes the reduced fuel
economy (as well as reduced power output).

As far as the potential for engine damage, if the octane is low enough
that the ECU can no longer retard the spark enough to compensate, or if
it gets to the point of dieseling, then yes detonation can cause engine
damage.

-Fred W<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

Hey everyone- Thanks...I am sticking with the higher octane, I just wanted hear what others thought. Everyone is correct, saving a few bucks at the pump is not worth ruinning an awesome machine. But at the same time, if the lower octane gas was not helping or hurting, then there is no reason to throw the money away. But since it reduces performance, milage, and could do some long term damage, then it is worth it. Thanks again
 >> Stay informed about: Do I need the expensive gas??? 

"dugies25" <UseLinkToEmail.TakeThisOut@AutoForumz.com> wrote
 > Hey everyone- Thanks...I am sticking with the higher octane, I just
 > wanted hear what others thought. Everyone is correct, saving a few
 > bucks at the pump is not worth ruinning an awesome machine. But at
 > the same time, if the lower octane gas was not helping or hurting,
 > then there is no reason to throw the money away. But since it reduces
 > performance, milage, and could do some long term damage, then it is
 > worth it. Thanks again

Exactly.

BTW, congrats on your purchase, have fun and visit here more.

Floyd<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

dugies25 wrote:

 > I am pretty new to this "Ultimate Diving Machine" experience. I want
 > to treat my car right, but I also don’t want to throw money out the
 > window when I don’t need to. My previous cars have never required
 > premium gasoline, but they have never been BMW’s either. I read in the
 > manul to use 91 octane or above to avoid knocking in the engine. But I
 > have also heard reports that unless you are driving a super high
 > performance vehicle that your car won’t know the difference between
 > 87, 89, or 93 octance gasoline. I have a 2003 330 CI, It is the most
 > high performance vehicle i have ever owned, but i don’t know if it
 > qualifies as needing the higher octane gas...and with the gas prices
 > today, if it doesn’t need it, I could save $5-$10 a week by getting
 > the lower gas. What does everyone think? Has anyone had experience
 > with knocking in their engine from lower octane gas?

Your engine has a compression ratio over 10:1 - that is definitely high performance land for an engine. It
needs 91 octane gas. What many people don't realize is that while the spark is retarded with lower octane gas,
it is also very likely that in many situations (pulling a hill, hot summer days, for example) this may not be
sufficient, so the next step for the DME is to richen up the mixture. Lower octane and retarded timing tend to
increase cylinder head temp - which the DME is monitoring - so it starts throwing in an overly rich mixture to
obtain some extra cooling from evaporation of the excess fuel. Now you dump this extra fuel into the catalytic
converter - guess what? It starts getting hot. Remember, all this can happen without any knocking. The DME
will 'try' to prevent knocking at all cost.

It's all dependent upon driving conditions, load, air temp, etc, but I sure wouldn't do it. Read an article
recently (don't remember where) where Steve Dinan went through the intricacies of providing adequate cooling
while testing cars on a dynamometer. The M5 he was testing ran the fuel mixture up to as rich as 9 to 1, if I
remember correctly, (as opposed to the 'correct' 14 to 1 ratio) during the test trying to keep itself cool -
even though he had a pretty good fan blowing air at it to simulate the effect of road speed cooling air flow.

From my own experience, our 91 octane here in CA is such junk that I will often get major brand gas that just
doesn't seem up to par. My 328 runs poorly until I drain that tank and fill with another brand. Any trip over
to Nevada or Arizona where I clean the tank of CA gas usually gives me better mileage and performance - until I
get home.

What would be really neat, and add greatly to these discussions, would be for someone in this group with an
OBDII scan tool to run a test using the real-time monitoring capability for spark advance and mixture ratio,
using 89 vs 91/93 octane gas. My money's on it showing a quite a difference in 'tough' situations - say
pulling up I-15 from Barstow to Vegas on a summer day.

Just my $.02

Frank<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

I just don't get it. You have spent a fair amount of dosh on a fairly new
car. You have clear instructions from the manufacturer what fuel to use for
optimum performance.

For the sake of 500 bucks or maybe a bit more per year you want to consider
contravening the instruction?

There is an excellent expression in German: Milchmädchenrechnung (milk
maid's calculation).

It just doesn't add up.

DAS

For direct contact replace nospam with schmetterling
---

"dugies25" <UseLinkToEmail.RemoveThis@AutoForumz.com> wrote in message
news:1_513265_0c6dd3587a443755212f0dcb0d3eb8f7@autoforumz.com...
 >I am pretty new to this "Ultimate Diving Machine" experience. I want
 > to treat my car right, but I also don't want to throw money out the
 > window when I don't need to. My previous cars have never required
 > premium gasoline, but they have never been BMW's either. I read in the
 > manul to use 91 octane or above to avoid knocking in the engine. But I
 > have also heard reports that unless you are driving a super high
 > performance vehicle that your car won't know the difference between
 > 87, 89, or 93 octance gasoline. I have a 2003 330 CI, It is the most
 > high performance vehicle i have ever owned, but i don't know if it
 > qualifies as needing the higher octane gas...and with the gas prices
 > today, if it doesn't need it, I could save $5-$10 a week by getting
 > the lower gas. What does everyone think? Has anyone had experience
 > with knocking in their engine from lower octane gas?
 >
 > --
 > Posted using the <a style='text-decoration: underline;' href="http://www.autoforumz.com" target="_blank">http://www.autoforumz.com</a> interface, at author's request
 > Articles individually checked for conformance to usenet standards
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 >> Stay informed about: Do I need the expensive gas??? 

"fbloogyudsr" <fbloogyudsr RemoveThis @nwlink.com> wrote in message
news:114gkpr7ueir380@corp.supernews.com...
 > "Somebody" <somebody RemoveThis @nospam.russdoucet.com> wrote
  >> "Troika" <lank RemoveThis @sympatico.ca> wrote
   >>> 91 or 93 octane you now drive a car not only a better vehicle but in
  >> order
   >>> to get better gas mileage
   >>> and performance and most of all stay away from the shop "dugies25"
  >>
  >> I don't belive that he will get any better mileage, nor fewer repairs, by
  >> using the correct grade of gas rather than an under-spec rating suchh as
  >> 89.
  >> Do you have evidence to the contrary? The only problem will be reduced
  >> performance.
 >
 > Wrong. He will also get less mileage, because the engine computer
 > will have to run the engine richer to keep the intake charge cool.
 > Retarded ignition timing will also result in less mileage, in addition
 > to lower performance.

Not enrichment of fuel mixture but retardation of spark. Same impact, lower
mileage. Whether the reduced mileage (at lower cost per gallon) is less
efficient in terms of miles per buck would be an interesting experiment.

R / John<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

dugies25 wrote:
 > I am pretty new to this "Ultimate Diving Machine" experience. I want
 > to treat my car right, but I also don’t want to throw money out the
 > window when I don’t need to. My previous cars have never required
 > premium gasoline, but they have never been BMW’s either. I read in the
 > manul to use 91 octane or above to avoid knocking in the engine.

Another point worth debating is the fact that the octane rating at the
gas pump says "minimum octane 91". This implies that the gas could be
higher octane but they are only guaranteeing 91.

I have a related question: Where is the gas mixed to give it a specific
octane rating? At the refinery or at the gas station? I ask because if
it is at the refinery (my assumption), do they send 3-4 different tanker
trunks to the stations for the different grades, one tanker with
different grades in different fuel tanks, or do they somehow mix it?

Lastly, how big of a difference (other than price) is there between 89
and 91 octane gas? Is 2 octane significant enough to even worry about?<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas??? 

dugies25 wrote:
 > I am pretty new to this "Ultimate Diving Machine" experience. I want
 > to treat my car right, but I also don't want to throw money out the
 > window when I don't need to. My previous cars have never required
 > premium gasoline, but they have never been BMW's either. I read in the
 > manul to use 91 octane or above to avoid knocking in the engine. But I
 > have also heard reports that unless you are driving a super high
 > performance vehicle that your car won't know the difference between
 > 87, 89, or 93 octance gasoline. I have a 2003 330 CI, It is the most
 > high performance vehicle i have ever owned, but i don't know if it
 > qualifies as needing the higher octane gas...and with the gas prices
 > today, if it doesn't need it, I could save $5-$10 a week by getting
 > the lower gas. What does everyone think? Has anyone had experience
 > with knocking in their engine from lower octane gas?

The few dollars saved per week will be partly eaten up in poorer gas mileage
me thinks. Not worth it in my opinion. I have a 330 and I wont put 87 in it
for any reason. I think the "savings" with 89 would not be significant
enough in the long run.

Jeff<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Do I need the expensive gas???