2007 X5 Can RUN on Regular Fuel - Page 2

mhainen · #11 01-27-2007, 01:31 PM

From the California Energy Commission. There is plenty more out there. Just do the research! If you have money to "burn"

then by all means proceed post haste

"Virtually nothing is gained by filling up with a premium or more expensive grade of fuel than the vehicle manufacturer has recommended, the experts say. And many of the same experts explain that drivers may not lose much performance from their cars by using a lower grade of fuel than recommended by the car manufacturer.
There is little difference in energy content of regular versus premium gasoline. They both contain about 111,400 British Thermal Units of energy per gallon.
The price difference, however, between the fuel grades is anywhere from 20 cents to 40 cents, depending on where you live in the United States. The experts' consensus goes against the long-held belief by thousand of drivers who fill up with premium only, or on every third or fourth trip to the pump. The idea is to fill up with premium every so often to clean out the engines or rev up the performance of older engines.
But according to the experts, this practice is like tossing quarters in a wishing well, since most engines are designed to operate on relatively low-octane regular unleaded gasoline.
Octane is defined as a fuel's resistance to knocking. There is no benefit if the octane is higher than what the engine needs. Engine knock occurs when fuel in a combustion chamber ignites before it should. This disrupts the engine's operation. But electronic knock sensors are now common and have nearly eliminated engine disruption.
The American Petroleum Institute says if you find that your car runs fine on a lower grade, there is no sense switching to premium. The Institute recommends following manufacturer's recommendation, but even those manufacturers say that it is more of a suggestion than a command. "

Sponsored Links

JCL · #12 01-28-2007, 08:24 PM

Quote:

Originally Posted by X5HogTown

A Toronto BMW dealer actually tells people to use low-test in the winter (via a little sign in Customer Service). Apparently, the gas companies put all the premium additives into low-test during the colder winter months. I assume this raises the octone level of low-test and you're basically wasting money buying high-test.

Anybody have first-hand knowledge of this practice?

Yes. My experience with the dealer in this respect is not in going to 87, but in going to 89, or mid-grade. It is not because the gas companies put more additives into their regular fuel during the winter and thereby change the AKI. For all intents and purposes the cleansing additives are the same between the various grades now, and the additives aren't changing the AKI. The reason for using mid-grade in winter is that in some conditions, owners report trouble starting on a winter fuel blend. Recall that premium is, by definition, harder to ignite. That is a little simplistic, but it will do. Essentially, in colder climates, mid-grade can run better than premium. You can notice easier starting. Your dealer is not the only one recommending that if an owner has trouble with starting on their local winter fuel, that they try mid-grade.

JCL · #13 01-28-2007, 08:46 PM

Quote:

Originally Posted by WagnerX5

NO regular is not fine. I don't know where you pulled the "CPU automatically adjusts..." thing from. Does the CPU recalculate based on O2 readings, yes, however via knock-sensors and timing control the engine can not compensate for the wrong fuel. Which if you're not using the owners manual recommendation, is the wrong fuel. You could also run just water in the radiator. The manual is there for a reason, and M or SAV has nothing to do with it.

Wagner, there is a little bit of scare tactics in your response, IMO. Regular MAY be fine. The trouble with drawing absolutes here is that the right fuel is not defined by the label on the gas station pump. There is an obvious correlation, but the right fuel is the one that has sufficient AKI so as not to knock, or cause noticable performance degradation.

Many consumers can not sense the above, so BMW, like other manufacturers, strongly recommends that they use 91 or 92, whichever it is, just so they can cater to the masses. It would take too much time and energy to have this discussion with every purchaser of a new vehicle.

A fuel that is labelled as 92 on the pump will typically have a range of absolute AKI test values, depending on how fresh it is, whether it is a summer or winter blend, how good a day the refinery was having, and so on. There may be a wide range of real AKI values, or a narrow one, with any particular supplier. Geographic factors in North America play a very large part in this.

The problem is that a fuel is not blended based on a theoretical formula. AKI is an empirical number. Testing a fuel several times (and it isn't an exact test) on a low speed, ultra-low tech, single-cylinder test engine, in a lab, produces results that are then compared to a fuel that is composed of a certain percentage of octane. It is never tested in a BMW engine to get that published AKI. Specifying that 92 is the 'right fuel' is simply agreeing with the BMW lawyers that they probably won't get too many consumers complaining if those consumers are instructed to use a fuel that the petroleum industry sells as 92 AKI.

Different engines will react differently to the same fuel with a certain AKI. Also, the same engine will react differently to different fuels that both have an AKI of 92, because AKI does not specify how a fuel will work in any particular engine, except for the single-cylinder test engine (using either the Research or Motor test methods)

There is nothing similar here to the example of running water in a BMW radiator and leaving out the required coolant conditioners. Those conditioners match a formula, and perform specific functions.

Yes, the owner's manual is there for a reason. That manual has many instructions that owners may or may not follow, at their own risk. One of them is not to use any aftermarket parts. Every mod that is discussed on this board is in some way going against what the manual says. It is up to the owner to decide what is the right thing to do.

I happen to agree with the comment about this not being an M car. The tolerances simply aren't as close as they are on a high-performance engine. There are broad safety factors. I may choose to use 89 AKI in my X5 occasionally, but I would also choose not to do so on an M5, because the consequences are greater, and the likelihood of there being any problems is higher.

Just my $0.02

JCL · #14 01-28-2007, 09:23 PM

Because we motorheads know who we are...

The Waukesha CFR (Cooperative Fuel Research Committee) engine first came out in 1928. It is a variable compression ratio, single cylinder test engine. The current production model has a crankcase that debuted in 1948, hence it is the 48 model. The current production model has the same combustion chamber design as the first model, so a fuel tested on a 1930 version of this engine will give the same result as on a test engine built this year.

All of the test engines in use around the world are still built by the Waukesha division of Dresser, to my knowledge. I could be wrong.

There are different configurations or versions of the engine for the Motor method, Research method, and cetane measurements (diesel). If you want to get an AKI for a fuel you need two engines, a Motor version and a Research version. They are either 600 or 900 RPM engines, approx 600 cc, with four carburettors so fuels can be quickly changed. The test fuel is compared to a reference fuel. Knock is sensed a variety of ways. If a fuel knocks at the same compression ratio, etc, as a reference fuel, it will be labelled as having that AKI. That is why fuels can behave very differently in modern production engines, as modern engines have a wide variety of combustion chamber shapes, injection technologies, etc.

I used a similar engine during my university days, many years ago. I suspect there are a few other members on here who have run octane tests themselves. Please chime in.

A photo of an early model is attached. Current models are basically the same, but get more complicated instrumentation.

So, when BMW says that we should use 92 AKI, it is because the fuels they tested in the X5 engine, when tested on this Waukesha lab engine, had similar AKI ratings as reference fuels with an AKI of 92 (allowing a safety margin for local fuel production variation). My point is that since the ASTM test does not dictate how any particular engine will respond with any particular fuel (it only compares results on this engine, under a single set of conditions), your experience will vary.

Wagner · #15 01-28-2007, 09:28 PM

Quote:

Originally Posted by JCL

Wagner, there is a little bit of scare tactics in your response, IMO. Regular MAY be fine. The trouble with drawing absolutes here is that the right fuel is not defined by the label on the gas station pump. There is an obvious correlation, but the right fuel is the one that has sufficient AKI so as not to knock, or cause noticable performance degradation.

Many consumers can not sense the above, so BMW, like other manufacturers, strongly recommends that they use 91 or 92, whichever it is, just so they can cater to the masses. It would take too much time and energy to have this discussion with every purchaser of a new vehicle.

A fuel that is labelled as 92 on the pump will typically have a range of absolute AKI test values, depending on how fresh it is, whether it is a summer or winter blend, how good a day the refinery was having, and so on. There may be a wide range of real AKI values, or a narrow one, with any particular supplier. Geographic factors in North America play a very large part in this.

The problem is that a fuel is not blended based on a theoretical formula. AKI is an empirical number. Testing a fuel several times (and it isn't an exact test) on a low speed, ultra-low tech, single-cylinder test engine, in a lab, produces results that are then compared to a fuel that is composed of a certain percentage of octane. It is never tested in a BMW engine to get that published AKI. Specifying that 92 is the 'right fuel' is simply agreeing with the BMW lawyers that they probably won't get too many consumers complaining if those consumers are instructed to use a fuel that the petroleum industry sells as 92 AKI.

Different engines will react differently to the same fuel with a certain AKI. Also, the same engine will react differently to different fuels that both have an AKI of 92, because AKI does not specify how a fuel will work in any particular engine, except for the single-cylinder test engine (using either the Research or Motor test methods)

There is nothing similar here to the example of running water in a BMW radiator and leaving out the required coolant conditioners. Those conditioners match a formula, and perform specific functions.

Yes, the owner's manual is there for a reason. That manual has many instructions that owners may or may not follow, at their own risk. One of them is not to use any aftermarket parts. Every mod that is discussed on this board is in some way going against what the manual says. It is up to the owner to decide what is the right thing to do.

I happen to agree with the comment about this not being an M car. The tolerances simply aren't as close as they are on a high-performance engine. There are broad safety factors. I may choose to use 89 AKI in my X5 occasionally, but I would also choose not to do so on an M5, because the consequences are greater, and the likelihood of there being any problems is higher.

Just my $0.02

Can't use a scare tactic till I have a way of making money off the deal

Anyway, my point is this.....millions of dollars were spent on engineering and in that it was determined that maximum performance and life could be helped by utilizing a specific grade of fuel....to me....I'd follow that logic.

motordavid · #16 01-28-2007, 09:28 PM

Outstanding Dig, Jeff!

I have done some casual reading: car mags, the net, etc.
on octane req's and that "engine" kept coming up in some
of the more esoteric links...I never dug further and supposed
it, tha engine, was used "then" and not now.

Very interesting...and now I can do a little more digging and
reading! Thank you.
BR, Ol'UncMotor

PS: 600 CCs with 4 carbs sounds like a few M'cycles I know!

JCL · #17 01-28-2007, 09:36 PM

Quote:

Originally Posted by motordavid

Outstanding Dig, Jeff!

I have done some casual reading: car mags, the net, etc.
on octane req's and that "engine" kept coming up in some
of the more esoteric links...I never dug further and supposed
it, tha engine, was used "then" and not now.

Very interesting...and now I can do a little more digging and
reading! Thank you.
BR, Ol'UncMotor

PS: 600 CCs with 4 carbs sounds like a few M'cycles I know!

Except that it only uses one at a time, and you switch between the carbs with what is basically a tap (turn one off, turn another on).

Low-tech doesn't begin to describe it.

There is a good Waukesha pdf on the web that commemorates decades of production, interesting reading.

JCL · #18 01-28-2007, 09:37 PM

Quote:

Originally Posted by WagnerX5

Can't use a scare tactic till I have a way of making money off the deal

Anyway, my point is this.....millions of dollars were spent on engineering and in that it was determined that maximum performance and life could be helped by utilizing a specific grade of fuel....to me....I'd follow that logic.

Point well taken. Does that also apply to following BMW's recommendations for oil changes (maximum performance and life, etc...)?

AzNMpower32 · #19 01-28-2007, 09:40 PM

Eh, we just run premium all the time in the X3. It's not that much $$$ over mid-grade in the end anyway.

Unfortunately, my dad forgot everything I said about ethanol in the X3 (and how it doesnt like it), and went to the Mobil that I know has 10% in its fuel. Now, I don't know if all gas in the US has E10 now, but I certainly don't remember having starting trouble when I filled up normally at the Texaco.

Today, I had to try three times just to get the X3 started from a cold start. Like literally I hold the key in "start" for 5 secs and the car just quits and I can't turn the key to "start" again, so I have to take the key out and retry.