Premium or Regular Gas ?

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This is being cross posted to alt.autos.bmw and alt.auto.mercedes because they get more readership than alt,autos.jaguar and the issue is the same for
some models of them.
I just picked up a 2003 X-Type with the 2.5 engine and only 3250 miles, yes that is correct, three thousand two hundred fifty on it. It is a long story not worth going into.
The owners manual says the car requires Premium Unleaded here in the USA. A person I work with has the same car and said he uses Regular NOT Premium and does not get any pinging and also gets the same mileage as when he used Premium. He claims that the computer retards the spark to prevent pinging and damage.
My question is will I damage the engine if I do the same.
Double Tap
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No. The 'person' is right. The engine has a 'Knock Sensor'. What might be called a pinking sensor, which advances or retards the ignition timing to suit the grade of fuel being used. In effect the ECU 'learns' the best ignition setting. Mike.
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I can't imagine why it would require premium. It is a rebadged and mildly reworked midsize European model Ford. You might get an immeasurable performance increase, but it truly would be trivial.
Nice car with a great look, but it is a Ford
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Your car is designed for premium fuel due to higher compression ratio. Stick with premium fuel.
Yes, car computer can retard the timing for lower octane, but fuel economy will suffer. You can try the mid grade to see if you get the same mileage... but not regular.
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Don't agree

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Because you don't know.
I do agree. There's no reason in the world why the engineers would specify a more expensive fuel if it wasn't better for an engine. Sure, regular will run but you may suffer consequences that you will not see and may not immediately comprehend.
wrote:

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Sorry, I do know. For a high performance car I would agree. KX8 = premium.
The X is just a little Ford. Nothing high performance about it at all.

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I'M WITH TOM on this topic.

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On Sun, 28 Jan 2007 00:03:20 -0500, "SharkmanBMW" <sharkmanbmw at gmail dot com> wrote:

Okay, and from where do you get the info that leads you to your decisions if you do know?

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If you use regular the knock sensor will retard timing to prevent engine damage. This will result in less power/mileage. You may not notice it however, unless you drive the car hard.
Vito

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As one who designed engines for many years, my take on it is to use the lowest octane you can that does not knock. I run plus in my E320 and C280. Regular makes them both knock during acceleration. Knocking is more prevalent during periods of high load (ie acceleration or very high speed) and when the engine is hot (ie summertime). Any effects on mileage are generally negligible.
EJ in NJ
ncle_vito wrote:

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On Sun, 28 Jan 2007 11:49:48 -0500, Ernie Willson

octane affects it? Thanks
Brake Specific Fuel Consumption Cylinder Head Temperatures Exhaust Gas Temperature Induction Air Temperature Internal Cylinder Pressure Rich of Peak Lean of Peak
I'd pay the closest attention to internal cylinder pressure and how it relates to the fuel burn. Feel free to confer with Tom, he says he knows.
Old Wives Tales not considered.

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On Sun, 28 Jan 2007 19:42:04 GMT, snipped-for-privacy@verizon.net wrote:

If an engine has to have a wider throttle opening and mass airflow + fuel at the correct mixture to produce X BHP then if the lower grade fuel has a lower calorific value and or burns hotter (less dense air) then more fuel is required to produce the same BHP as your test started with.

Unleaded fuel (gas) burns hotter and faster than leaded gas therefore the temperature is hotter. Leaded fuel burns slower therefore the ignition could be advanced so the maximum expansion occurred at the exact moment the piston started its downward travel and continued expanding until spent. A bit like modern gun powder is a propellant which expands continually pushing the projectile (bullet) down the barrel whereas the real gunpowder (black powder) was a BANG and go situation.

See first - unleaded gas burns faster and more raggedly and hotter (BANG) therefore exhaust gas temp higher and this is needed to ensure the platinum in the cat works.

The colder the better for power but the more dense (cold) it is the more fuel is required to enable the engine to run. Ambient is Ok but depends where on the planet you are. The less air the less fuel = less power.

See Cyl Head Temp. Unleaded = Bang and go whereas leaded = push and keep pushing.

Sir Hugh of Bognor
The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it!
Hugh Gundersen snipped-for-privacy@h-gee.co.uk Bognor Regis, W.Sussex, England, UK
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snipped-for-privacy@h-gee.co.uk wrote:

And there was me thinking it was the *size* of their toys.

The Jaguar group, I presume?
Ximinez
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On Mon, 29 Jan 2007 18:01:05 +0100, The Spanish Inquisition

Sorry to say my friend --- NO NO NO BMW E38 V8 '97.........
Jaguar cars are Ok when they are Jaguar and not FORD MONDEO reskinned. I will give that it's a nice car with all the usual Jag leather and wood but it is all looks.
Now when we move up a notch - the UK EDSEL is the "S" Type neither real retro (Dodge Charger/Barracuda) nor attractive styling. The V8 4.2 DOHC is a nice engine and better than the Real 6 pot Jaguar but the car is all wrong.
The KJ8 is still the one to buy but NOT the supercharged one - nice idea in Texas where gas is dirt cheap??? but not in the UK or Euroland.
I'll stick with a REAL engineered car BMW - Merc are far too like a TAXI and all the 'performance' models are usually V6 or like something out of a Detroit drug induced theme party - Star Wars????
Sir Hugh of Bognor
The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it!
Hugh Gundersen snipped-for-privacy@h-gee.co.uk Bognor Regis, W.Sussex, England, UK
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Octane number has no effect at all on any of the things you mention. Octane does not affect fuel heating value (fuel energy content). Since this is so misunderstood let me explain what an octane number is/means.
First lets understand what knocking (preignition/detonation) is. Consider a cylinder that is charged with air and fuel at a proper mixture for combustion. The spark plug starts a fire in some area of the cylinder. A flame front starts out from the spark plug and it continues until the flame front crosses entire combustion volume and the fuel is consumed. This is the normal situation, where no detonation occurs. The pressure rise is steady and reasonable.
On the other hand combustion can occur in the following manner. A spark starts the fire, a flame front starts across the cylinder, raising the pressure and temperature everywhere in the cylinder. The mixture in some area of the cylinder sits there long enough that its "delay time" is exceeded. (Delay time is the time lag between when a fuel air mixture gets to the temperature/pressure conditions which would cause it to detonate, and when it actually goes off). To continue..Because of local conditions this volume of fuel air that has not been ignited by the flame front decides to go off all at once. This is called detonation or preignition and it is heard as knocking. The rate of pressure rise is instantaneous and most violent. If an engine is run in this condition for any sustained period it will be destroyed.
It was found years ago that if Octane, a liquid fuel was added to gasoline it would increase delay time and retard the the onset of detonation. Put another way Octane increases the "delay time" so that the flame can get to the area before the fuel detonates.
The Octane number of a fuel reflects the relative amount of Octane to gasoline which produces the same knock characteristic as the fuel being tested. This is tested in a research engine, under very controlled conditions. Octane is expensive and therefore additives were developed that increased fuel delay time just like octane does. In fact some additives are so effective they are more effective that 100% Octane, and this is why some gasolines have octane ratings over 100.
Provided an engine is not knocking, the octane rating of the fuel will not effect any of the things you mention. If the engine is knocking it should not be operated at those conditions and the question is moot. When an engine is knocking, power falls off, and fuel consumption increases. Cylinder pressures and temperatures skyrocket.
Gasoline alcohol mixtures can sometime exhibit high octane characteristics, however, because alcohol has a heating value lower than gasoline, high octane gasolines that use alcohol for octane control will have higher fuel consumption (lower miles/gallon) than straight gasoline.
HTH, EJ in NJ
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I inadvertently said that the octane number reflects the relative ratio of Octane to gasoline. It is actually the ratio of Octane to Heptane. Octane has a long delay time, and Heptane has a short delay time.
EJ in NJ
Ernie Willson wrote:

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You also think it is just a Ford. Just because it shares some components with a Mondeo does not mean it is the same car with a different skin.
If the manufacturer recommends a specific grade of fuel why not follow it? It is not as if Ford sells petrol, is it?
DAS
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Wow, reviving a dead thread, are we.
I do think it is a Ford. It is a Ford. It shared more than components. It's the same car with prettier bodywork.
But honestly, I really don't care.

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I don't think being like the Mondeo is necessarily a bad thing.
I lived in the UK from 1994 - 1997 and one of the cars I had was a leased Mondeo II 24v V6. I liked the car. It was quick, nimble and had good utilitarian features as well as being reasonably economical. I think being like the Mondeo is a plus, not a minus. The Mondeo was far and away superior to the Sterling/Rover I had the time I was there before in the early 90's.
When I turned it in it still had the wheel covers on the left hand side of the car too.
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