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pistik View Drop Down
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  Quote pistik Quote  Post ReplyReply Direct Link To This Post Topic: gas mileage
    Posted: 06-Feb-2007 at 18:03
Of course the gas mileage wasn't priority with W8. And it shouldn't be for that you have TDIs and 4cyl....

The thing is that here in Canada on the normal gas stations you have selection of 87, 89 and 91 octane.
There are gas stations which carry 94 octane but only few of them here in Toronto. It makes it difficult to drive and look for your 94 octane gas station...

And then I guess we should not be suprised here in north America that we have bad gas mileage with even with "premium fuel" 91 octane.

Back in Slovakia 5y ago I used to put 98 octane only in to my GTI...
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  Quote B5crazy Quote  Post ReplyReply Direct Link To This Post Posted: 06-Feb-2007 at 19:44
Just remember that in Europe petrol octane is calculated buy the RON method. In the US octane is the average of the RON and MON methods (R+M)/2. The MON numbers are about 8-10 less than the RON numbers. Thus, gasoline in the US may have an octance number of 93 and in Europe the same fuel would have an octane of 98.
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  Quote Garfield Quote  Post ReplyReply Direct Link To This Post Posted: 06-Feb-2007 at 19:57
Jeez they sell some nasty stuff in Canada eh ...

Do they sell Methanol on the forecourt too?

There is no way you can be running a decent ignition advance on such low octane values it would blow the engine to bits. Typically you lose 1 degree of advance for every octane point, so if design says 10 degree advance is the optimum ignition point for 98 octane and you chuck in 87 Octane your car will likely calculate a 1 degree retarded ignition !!, given the speed at which the flame face travels that could cost you BIG in the power stakes if say perhaps you lose 20% of the downstroke before any real power kicks in you can see the problem and wastage. Need to get that fire going BEFORE the piston gets to the top so the power kicks in just after TDC extracting all that wonderful expansion as rotary motion.

Why so low ????

What do VW say about using such Octanes?

I can now get 99 octane in the form af VPower from Shell here in the UK - of course it is expensive but as I said it makes a difference. It is something you need to plan though because the places that sell it aren't always handy, hence I generally keep my car topped up whenever I see one rather than waiting for the 'oh sh1t light' because if your cars are like the BMW once that light is on you don't go far, I hate my tank below a quarter anyhow and regard the quarter as the empty mark.

Any of you guys tried any of the octane boosters such as the Power Pill ?? may be worth a try to see if it helps.
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  Quote pistik Quote  Post ReplyReply Direct Link To This Post Posted: 06-Feb-2007 at 20:17
Originally posted by B5crazy

Just remember that in Europe petrol octane is calculated buy the RON method. In the US octane is the average of the RON and MON methods (R+M)/2. The MON numbers are about 8-10 less than the RON numbers. Thus, gasoline in the US may have an octance number of 93 and in Europe the same fuel would have an octane of 98.


Cool...
I started to read about octanes and I'm glad I learned something new.

Now I can explain to all my fiends that there is no actual difference between US fuel and Europe fuel in terms of octanes...
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  Quote B5crazy Quote  Post ReplyReply Direct Link To This Post Posted: 06-Feb-2007 at 20:23
I want to get chipped which should also help my mpgs. It's just that GIAC hasn't mapped a 2004 6MT W8 ECU. However, I'm working wih a tuner to rectify it.   
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  Quote w8cmp Quote  Post ReplyReply Direct Link To This Post Posted: 07-Feb-2007 at 03:15
Originally posted by Garfield

I can now get 99 octane in the form af VPower from Shell here in the UK - of course it is expensive but as I said it makes a difference. It is something you need to plan though because the places that sell it aren't always handy, hence I generally keep my car topped up whenever I see one rather than waiting for the 'oh sh1t light' because if your cars are like the BMW once that light is on you don't go far, I hate my tank below a quarter anyhow and regard the quarter as the empty mark.


I'm the same...I haven't used anything other than Shell VPower 99 Octane in my W8 since Shell launched it. I keep accurate calculations of MPG on each and every fill, and I have been getting better mileage per tank (and better power delivery) since using VPower. I won't use any cheap low octane cr*p unless it's a real emergency...and I haven't had to yet...
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  Quote craig Quote  Post ReplyReply Direct Link To This Post Posted: 07-Feb-2007 at 13:48
Originally posted by Garfield

Jeez they sell some nasty stuff in Canada eh ...


Actually, Sunoco Gold (94 R+M/2) is slightly higher octane than (the old leaded) EuroSuper 100.

Normal premium (91 R+M/2) is about the same as Euro 98.

Of course, that's an approximation, not a direct conversion - Google away if one wants to understand why.

Note also that European W8's have a higher compression ratio than US/CDN W8's. Power is also slightly higher in the Euro ones. I suspect that the camshafts are also different (or the variable cam timing), as the torque curves are different. US/CDN W8's have a significant torque peak at 2700rpm (or so) that the Euro motors don't have.

I am guessing that the lower CR in the US/CDN model is so that the W8 can run on regular (87 R+M/2) unleaded without ill effects or too much retarding of the ignition timing. I use regular most of the time, especially in winter - at over 10 cents a litre cheaper, it adds up.

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