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Specific discussion about the E89 2009 Z4 (sDrive35is, sDrive35i, sDrive30i, sDrive23i)
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Buckz
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Post by Buckz » Wed May 24, 2017 8:42 am

Every 2-3 tanks I fill up with vpower.. last 3 tanks were vpower only and I've personally noticed 0 difference, can't see inside the engine tho ;)

Next tank is gunna be a super from supermarket but had no issues with 95.
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Post by Nick_in_Suffolk » Wed May 24, 2017 9:10 am

Doesn't the lower octane stuff contain relatively more ethanol (?) than the higher octane stuff? And ethanol burns at a higher temperature?

I know that even in my little 850 Mini I now need to run the higher octane fuel just to avoid severe detonation when the engine is under load (most of the time). The same is true of the Alfa we have.

It just seems natural to run the higher octane fuel in the other 2 modern cars. It's only a small extra cost per tank and amounts to less than £200 per year.
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Post by Matt64 » Wed May 24, 2017 10:24 am

Hmm this old chestnut again...

With my home Mapped turbo cars I use SUL, without a doubt. Purely from the 'insuring against pre det' argument.
With the Zed, I have owned for about 6 months, until recently, every drop of juice I put in it was SUL. I recently filled with 95 Ron (accidentally) and strangely found my mileage slightly better (go figure). 99ron=32mpg avg , 95ron=36mpg avg. No noticeable determination in performance and my det detector certainly isn't pinging.
I'm going to try a few tankfuls of the cheaper stuff for the sake of, very unscientific, experimentation. If anyone is interested I'll let you know how it goes.
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Post by lordgrover » Wed May 24, 2017 10:27 am

Busterboo wrote: Tue May 23, 2017 9:46 pm BMW say use 95 in the 35iS, so I do. :)
Doesn't it say recommended minimum is 95?

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Garvin
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Post by Garvin » Wed May 24, 2017 10:43 am

The higher the octane rating then the more the ECU can advance the ignition and the engine can run more efficiently. This is hardly noticeable in NA engines but can make a very noticeable difference in turbocharged engines. This does generally increase the performance of the car.

In theory this will increase mpg but only if all other things are equal e.g. speed and acceleration kept the same. In practice most enjoy the increased performance, particularly improved acceleration, so the improved mpg doesn't really come to pass.

Vendors claim better additives in their SUL re engine cleaning and whilst this is certainly true between premium and supermarket brands I'm not convinced that there is a substantial difference between regular and super for the same brand.

You pays your money and takes your choice.
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Post by ronk » Wed May 24, 2017 11:03 am

lordgrover wrote: Wed May 24, 2017 10:27 am
Busterboo wrote: Tue May 23, 2017 9:46 pm BMW say use 95 in the 35iS, so I do. :)
Doesn't it say recommended minimum is 95?
35is Info on fuel flap (Sept 2016)
IMG_4930.JPG
IMG_4930.JPG (267.17 KiB) Viewed 666 times
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So I bought a 35is with all the toys to play with. :thumbsup:

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Post by Yorkie Z » Wed May 24, 2017 11:10 am

ronk wrote: Tue May 23, 2017 7:52 pm Have a search on the forum for previous posts - You will find every answer under the sun!
God this a million times. It's like ground hog day.
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Post by ronk » Wed May 24, 2017 11:36 am

I have a PDF file on the computer produced in respect of Tesco premium petrol (Monentum) - from memory it's a proper scientific report based on proper measurements and not just random observations and hunches.
I will dig it out and post asap .
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Post by SonnyA85 » Wed May 24, 2017 12:23 pm

forget ron rating for a second here event though they have a knock sensor and will adjust.

Tesco 99 momentum has 4 times the additives than normal tesco fuel - these additives help keep your internals cleaner. proof of this has been shown at various car shows with cameras inside of engines that have used either fuel wholly for a number of miles.

then you do certainly get added benefit of a few more mpg so it evens out in terms of cost of the fuels.

my problem is that the only garage near me or on my route is an asda. i'd prefer it was tesco for 99 momentum or a BP for ultimate.

consensus is if you have a half decent car buy premium fuel. if you drive a run of the mill cheap car then don't bother. so i try to use premium whenever i can in the z4. the wife's mini gets asda every time with the odd tank of BP ultimate to give it a bit of a clean, however it is mainly asda in the mini 99% of the time.

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Post by Dave1971 » Wed May 24, 2017 12:52 pm

A few years back I remember watching a test on 5th Gear, can't remember all the cars they tested but it ranged from a Yaris to a Scooby. The nuts and bolts of it was if you run a grandma's shopping trolley then don't waste your money but if you have a performance car, particularly a turbo/supercharged car then it does make a difference.
Zed No 1 2004 e85 Z4 2.2 se
Zed No 2 2007 e85 Imola Red Z4MR
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Post by brittas » Wed May 24, 2017 1:47 pm

Yes that 5th gear test gave 4 BHP increase on a turbo car. V power in mine. That 4 bhp might come in handy at the traffic lights one day :evil:

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Post by lordgrover » Wed May 24, 2017 2:21 pm

ronk wrote: Wed May 24, 2017 11:03 am
lordgrover wrote: Wed May 24, 2017 10:27 am
Busterboo wrote: Tue May 23, 2017 9:46 pm BMW say use 95 in the 35iS, so I do. :)
Doesn't it say recommended minimum is 95?
35is Info on fuel flap (Sept 2016)
IMG_4930.JPG
That would suggest Shell V-Power is above the recommended 91-98...
That's interesting, I'll check my 35i if/when I finally get it back.

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Post by IRD » Wed May 24, 2017 5:22 pm

If you read the 'Honest John' motoring column in the Telegraph he is a big fan of the better quality higher octane fuel. He claims it helps to keep the engine clean and improves mpg. On the whole what he writes is sensible and his advice is usually sound. I don't know whether I am just a sucker but I use it in the Z4 but not in the everyday car.
whether it lives up to it's claims I don't know.

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Post by Busterboo » Wed May 24, 2017 5:48 pm

BMW 2010 Owner's Handbook (23i, 30i, 35i, 35iS) Munich, pub. BMW

page 189

"It is recommended to use unleaded premium grade petrol with 95 RON."

"Unleaded fuel qualities with 91 RON and higher are permitted."

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Post by Maniac » Wed May 24, 2017 10:22 pm

Sticker or not, I reiterate I've done this test on a dyno and premium fuel made more bhp.

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