Premium or Regular Gas ?

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I never said it was a bad thing. Great cars. Considering one for my teenagers first car, since it is AWD. People are reading things into my posts that weren't there.
My only point was that it isn't an XK8 and the performance difference of regular vs. premium would be really trivial in this car.
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Hi Richard,
My comments were aimed at the larger audience rather than you.
I think that if the engine internals (compression ratio, computer software etc.) are indeed the same, you are correct.
However, I believe that the only engine block is shared (in the 3.0 liter 227 hp engine) and the x-type has jaguar high compression heads, ignition, fuel system and computer management. The engine (my understanding) is built by ford on a separate assembly line. This may account for the discrepancy?
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Been away....
DAS
For direct contact replace nospam with schmetterling
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I love it when dead threads are revived Double Tap
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What's the engine's compression ratio? If 10:1 or higher I'd used Premium, perhaps cheat a bit with mid grade in cool weather, but not hot weather. Higher ambient temperatures bring an engine that much closer to pinging so premium is needed then to prevent that pre-ignition.
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It's 10.5:1, so on the borderline. 227hp out of 3 liters.
You could safely run either. "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote in message

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US Premium gas is about on par with Euroland/UK regular unleaded. Or in other words your regular wouldn't pass the UK/Euroland acceptance test (not gov). However having said that you will find that the engine control system ECU will compensate for any type of crap fuel that will actually allow the engine to run but the quality of the gas does play a part in the power output and as I said the US lower quality gas is rather low quality and your high grade is about the same as our cheaper grade. Anyway, you pays your money and takes your choice.
Why didn't you buy a BMW?
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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wrote:

Hugh, U.S. premium is 93 (R+M)/2 octane which = 98 RON.
So your UK/Euro premium is better than 98 RON? Or are you confusing sea level U.S. 93 premium with the U.S. 89~91 used in high altitude areas?
Tom K.
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wrote:

He'll get right back to you on that, once he finds someone who actually knows the answer ;-)
/daytripper '00 s4 6spd
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wrote:

Compliments of Wikipedia, he seems to have it backwards:
http://en.wikipedia.org/wiki/Gasoline
"Different countries have some variation in what RON (Research Octane Number) is standard for gasoline, or petrol. In the UK, ordinary regular unleaded petrol is 91 RON (not commonly available), premium unleaded petrol is always 95 RON, and super unleaded is usually 97-98 RON. However both Shell and BP produce fuel at 102 RON for cars with hi-performance engines, and the supermarket chain Tesco began in 2006 to sell super unleaded petrol rated at 99 RON. In the US, octane ratings in fuels can vary between 86-87 AKI (91-92 RON) for regular, through 89-90 (94-95) for mid-grade (European Premium), up to 90-94 (RON 95-99) for premium unleaded or E10 (Super in Europe)"
Our regular is 89, so 94-95 RON. UK regular is 91 RON. 87 can be found at bargain places, but not easily, at least where I live.
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wrote:

Bognor Regis, W.Sussex, England, UK
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Jeff,
I have been following the thread since my original post. I like your suggestion and will try it.
Double Tap
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(snip)
I agree with your logic and plan to test 87 PON mileage against the 93 I normally burn in my E46 - as soon we no longer have the "reformulated" winter gas. But I'm not really tempted by 89 PON as it's 10 cents more than 87, but 93 is only 10 cents more than 89 (in my area). In other words, by the pricing, "mid-grade" should be 90, not 89. Also, a new phenomena is "off brand" stations charging a differential of only 12 or 13 cents between 87 and 93, making the 93 even more of a bargain.
The manual for my BMW R1200RT motorcycle (12:1 compression) actually states that rated hp drops from 110 to 101 when the knock sensor retards the timing because of lower octane.
Wouldn't it be nice if EPA mileage figures specified the test octane on those cars which call for above regular grades?
Tom K.
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What a great and informative discussion of this critically important issue!
My two bits worth:
Re: using lower grade fuels. I found the following in an article on the Internet, for what it is worth:
"... there are fuel refineries across the country that will occasionally blend in bigger percentages of the inexpensive and very plentiful alcohol. It is said that some of these blends can contain as much as 15 to 20 % alcohol. Is this legal? ... probably not. However in a world of discount gas stations located in outlying areas, a don't ask don't tell policy is in place when the price is right. If an unknowing motorist buys a load of 15% - 20% alcohol fuel, his car starts a little harder and runs a little lazier. How can you know the true content? ... you can't. This underlines the need to buy fuel at a name brand retailer, or a station that you are familiar with.
"Another complication of alcohol is the high solvency. That is, it has a lesser lubricicity than the fuel it is being blended with. This higher solvency literally washes internal engine surfaces that require a presence of lubrication.
"The last significant complication with alcohol is that it attracts water. That is to say that it literally draws water out of the surrounding atmosphere into the fuel. This drawn-in water then enters the engine along with the fuel and oil. While the percentage of water content is low, it further contributes to the internal "washing" of surfaces needing lubrication. Blends that contain more alcohol can attract more water."
A final note: I use Chevron 94 Octane (the highest rating available in Canada) in my 2001 VDP. Chevron contains Techron, which has been formulated to remove potentially harmful deposits from injectors, intake valves, and combustion chambers. Currently it costs $1.11 a litre -- about 10 cents a litre more than 91 Octane and about 12 cents a litre more than 87 Octane.
Alan Strickland Victoria BC Canada

than
between
states
timing
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You might want to check the recent state law changes in your area. In my state, Maryland, ethanol is now virtually mandated (see link )and has replaced MTBE for the "reformulated" gas we get from November to March. From what I can tell, my mileage is a bit worse and the pumps are not so labeled!
http://www.mde.state.md.us/ResearchCenter/Publications/General/eMDE/vol2no4/alternativefuels.asp
Tom K.
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wrote:

Bognor Regis, W.Sussex, England, UK
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This debate is more fun then an oil debate. I say, if it makes you happy, use it. I know for a fact that if I set the timing on my 84 500SEL (yes, it is adjustable) for maximum advance with no knock and use preimium, the engine runs better (more power and smoother) and gets better mileage. If I retard the timing and use regular I can feel a difference more in smoothness but also in power. That alone is enough reason for me to use the the premiium. Mileage is better with the premium by about 2 mpg. I don't know if that makes it cheaper per mile or not, but I don't care if it makes me happy. I, for one, am not going to dispute what the MB engineers recommend. They designed the engine and are far smarter than I am in that field. Paul

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