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Another fuel thread - bear with me...

Discussion in 'New A3/S3 (8V Chassis)' started by Si_S3, Jul 31, 2014.

  1. Mdritchie
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    Mdritchie New Member

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    [Aug 2, 2014]
    I've read that Momentum 99 gets its high octane rating via a high bio-ethanol content which gives the fuel a much lower calorific value and really nails your fuel consumption. Any idea if that's true?
    #41
  2. The Challinor
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    The Challinor Well-Known Member

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    [Aug 2, 2014]
    Interesting observation about the fuel mix, I've not heard of that before.

    In terms of performance not noticed anything between V Power and Momentum, it's been discussed at length over the years in every car forum around. Switch to Tesco as a lot more of them locally, club card, offers, etc.

    Now bear in mind I drive a S3 ( 8P ) but to be fair not noticed anything either way as in it being much better or worse. If I take my time cruising at 60odd I can get 35mpg, averaging around 27ish.

    I maybe get a few extra mpg but the main reason for using it is for performance based reasons.
    #42
  3. Mdritchie
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    Mdritchie New Member

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    [Aug 2, 2014]
    Shell is pretty handy for me and they do a good coffee and Danish for £3 so I stick with them :)

    I wish I could remember who did the fuel economy tests. It was a well conducted experiment with Vauxhall Astra VXRs running different fuels, they looked at dyno outputs and fuel consumption and came to the conclusion that using super grade in these types of engines (small displacement, turbo charged, high output) was no more expensive and possibly cheaper.

    So my car runs tip top, it probably cost me at worst a negligible amount more and I can get a decent coffee at the same time. No brainer?... Well other than the fact my coffee and Danish budget has gone sky high ;)
    #43
  4. cilurnum
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    cilurnum Member

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    [Aug 2, 2014]
    I'm in the UK so yes, 95 is 'standard' for me and has been for some time in this country. However, 95 is by no means unrefined 'cheap' fuel and......I just have issues with manufacturers who weasel their way through wording to try and cover up their problems. It certainly shouldn't be happening on an expensive car people are paying a good premium for. It isn't even their high performance engines they do this on, it's all their TFSI engines (certainly when I last looked).

    I haven't used V Power for some years, but I can remember filling up once when I was desperate in a really bog standard 1.6 Astra Club, 115PS, nothing special at all. I have to say the effect was incredible. I wouldn't fill up purely for the economy reasons but that fuel turned what was otherwise a totally boring car into something incredibly smooth and enjoyable. I used to have a Shell garage not far from me but now it's BP.....

    Nope, but I certainly wouldn't want to shove additives in myself and these engines are way to complex now. That's why the fuel companies have massive chemistry departments.
    #44
  5. The Challinor
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    The Challinor Well-Known Member

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    [Aug 2, 2014]
    #45
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  6. cuke2u
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    cuke2u Well-Known Member

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    [Aug 2, 2014]
    Nice and sunny here, personally I am highly suspicious of any claims made about these fuels other than subjective evidence from drivers who claim they 'feel' a difference.
    #46
  7. The Challinor
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    The Challinor Well-Known Member

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    [Aug 2, 2014]
    #47
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  8. cuke2u
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    cuke2u Well-Known Member

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    [Aug 2, 2014]
    Yup 6.2% of 30mpg = 1.85 I do not trust companies testing their own products...
    #48
  9. J4MMYz
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    J4MMYz New Member

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    [Aug 4, 2014]
    Hi guys, this is a good little post as i'm most OCD with good fuels in cars, in my current 1.4 naturally aspirated I did use premium but didn't notice a notch of difference so I use normal.

    Can anyone answer the question of is there much point in filling a 1.4 TFSI 150ps petrol engine with premium? Being Shell V-Power, what octane rating is the normal against premium if anyone knows that also?

    I would imagine there would be a good side to fill it with premium, being supercharged and turbocharged but it is only a 1.4, so maybe no point? Am not too familiar on the technology of that, all a bit new to it.

    Cheers.
    #49
  10. The Challinor
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    The Challinor Well-Known Member

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    [Aug 5, 2014]
    Have a good read through this thread mate and the links I've posted.

    In short I'd put momentum in yours yes, normal is 95, momentum is 99.
    #50
  11. cuke2u
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    cuke2u Well-Known Member

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    [Aug 5, 2014]
    Waste of money, no gain at all....
    #51
  12. Mdritchie
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    Mdritchie New Member

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    [Aug 5, 2014]
    Based on what evidence? I seems quite plausible to me that it could make a difference as it seems to in many small displacement turbocharged engines. It's surely a question of whether it makes significant enough of a difference to warrant it and that's probably going to come down to personal choice. You're not going to break it with 95, you're not going to get a huge increase in bhp with 98/99, improved fuel economy might balance out some or all of the additional cost though.

    For me, I do 10k miles per annumn and I'm paying £450+ per month for my PCP, a few extra quid a month for super grade is not a huge part of my motoring costs. I know my fuel isn't holding the engine back in any way, I'm following Audi's recommendation and hopefully I'll get back some of it back by squeezing out a few more miles per tank. If I don't I'm not losing sleep over it.
    #52
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  13. Mdritchie
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    Mdritchie New Member

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    [Aug 5, 2014]
    "Premium" is "normal" in the UK and is 95RON.
    The higher octane stuff is generally called "super" grade. V-Power, Momentum 99 etc.
    #53
  14. J4MMYz
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    J4MMYz New Member

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    [Aug 5, 2014]

    Ahh, sorry, I did read through for some way but obviously not far enough ;) thanks.
    #54
  15. terapati
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    terapati New Member

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    [Aug 5, 2014]
    I'm looking forward to order a S3 Sedan through the end of the year. I'm reading reviews and other S3 8V issues here and this forum is helping to learn a lot, thanks guys. Here in Turkey, we have a serious fuel quality problem. We don't have 98RON, we used to have 97RON which was Shell V-Power Nitro. I don't know exactly why but this is not available right now. 95+RON with additives is the best option that we have at the moment. You might know that some countries can not receive S3 Sedan with 300HP and here it is coming with 285HP. I just wonder, if I use the car with that unknown 95+RON fuel, how it is gonna effect the overall of the car? I mean engine's condition in long time, power etc. Moreover, it doesn't make sense to spend that much money for far less power than 300HP. What do you think and suggest guys?

    Thanks in advance.
    #55
  16. The Challinor
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    The Challinor Well-Known Member

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    [Aug 5, 2014]
    No worries mate, as you can see it's a heated debate !
    #56
  17. cuke2u
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    cuke2u Well-Known Member

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    [Aug 5, 2014]
    What evidence have you got that it will under real driving condition, there is none out there I've seen that has convinced me to use anything other than supermarket fuel....
    Last edited: Aug 5, 2014
    #57
  18. cilurnum
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    cilurnum Member

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    [Aug 7, 2014]
    Overall, I would agree. I have V-Power in a petrol right now for the first time in years and it's made driving quite a bit more pleasurable and much smoother, but I'm not seeing any appreciable gains in economy.

    However, the manual for all TFSI and most direct injection engines tells you that even though it will run on standard fuel it is recommended to run on super, and that's the fuel you should be using. They word this specifically in the manual to cover themselves. Too many direct injection engines have had knocking problems over the years that manifest themselves into a broken engine (the pistons can basically end up going conical) after about 60,000 miles or just when the car gets out of warranty, so yes, you are likely to break your car running on standard petrol. It's happened and well documented - and this is any direct injection or TFSI, not just performance engines.

    Frankly, I couldn't justify a petrol engined car, even if it is cheaper to buy, when I would have to spend money on fuel that's more expensive than diesel and where I might very well have to fork out for a new engine in a few years.
    #58
  19. cuke2u
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    cuke2u Well-Known Member

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    [Aug 7, 2014]
    What manual are you referring to as I've not seen anything like what you've stated in mine. Thing is, if my engine was going to self destruct after 60,000 miles because of using 95 Ron I'd be taking the manufacturer to task because the inside of my petrol flap quite clearly states my engine can run on it and there is no warning that it could cause any damage otherwise. There are plenty of engines around of exactly the same design that have used 95ron and have done over 100,000 miles and I am sure all manufactures test their engine to destruction using fuel that has a lower Ron rating.
    You do know that all modern engines have their ignition and valve timings controlled electronically and have anti-knock sensors because you seem to be suggesting that they don't.
    One last thing, I sell my cars when they get to about 30,000 miles, or less, anyway..
    #59
  20. cuke2u
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    cuke2u Well-Known Member

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    [Aug 7, 2014]
    More about knock sensors:
    " A knock sensor allows the engine to run with the ignition timing as far advanced as possible. The computer will continue to advance the timing until the knock sensor detects pinging. At that point the computer retards the ignition timing just enough for the pinging to stop.*


    The knock sensor responds to spark knock caused by Pre-detonation of the Air/Fuel mixture. As the flame front moves out from the spark plug ignition point, pressure waves in the chamber crash into the piston or cylinder walls resulting in a sound known as a knock or ping. This is caused by using a fuel with a low octane rating, overheating, or over advanced timing. Sometimes it can be caused by hot carbon deposits on the piston or cylinder head that raise compression. A knock sensor is comprised of Piezoelectric materials; Crystals that when impacted, generate a voltage (same idea as a BBQ ignitor). This voltage is monitored by the computer, and when an irregularity is detected, the computer corrects timing in VVT (variable valve timing) engines, or triggers a DTC Diagnostic Trouble Code) in older vehicles."
    Of course this takes place in a split second before any damage can occur....
    #60
  21. cilurnum
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    cilurnum Member

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    [Aug 7, 2014]
    Your manual and flap might state that it CAN run on 95 but the RECOMMENDED fuel is 98. That's how they're weaselling it. There have been too many documented cases of direct injection petrol engine problems over the years to dismiss this. Look for that key word - recommendation.

    I'm not suggesting they don't just that in the case of direct injection engines whatever they're doing historically hasn't been enough, and it is a known problem regardless. Anti-knock systems can only do so much and you'd rather they weren't relied upon. Mercedes had terrible problems with their DI engines and VAG continued in that vain. I suspect they're pushing the boundaries too much for the sake of fuel economy and performance. The pistons have a tendency to cavitate over time with detonation at high revs under certain load conditions causing wear and tear. Cold compression problems are usually the first sign.

    If you have one, service regularly. If you see HPI, IDE, SCI, GDI et al - avoid. Add FSI to the list.

    This happened quite a bit on the old overstressed 1.4 100HP engines some years ago and it's a characteristic of the engines generally because people forget they are under quite a bit of pressure to get the performance and economy they do from such a small displacement. You have to work them to get the advertised power. The cyclinder on demand engine in the mix just sounds like a bag of spanners waiting to happen to me. Diesel engines have had their DPF and other problems but at least you had a fighting chance of catching those and they've largely been mitigated. DI engines are always going to be under pressure.
    #61
  22. A3_Rider
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    A3_Rider Member

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    [Aug 7, 2014]
    I remember this argument nearly five years ago now, still hasn't budged much!!

    In terms of real world pricing for 10k miles a year its about £170 more per year (or £15 per month) for peace of mind. If the price difference affects you I see no harm in the standard fuel, for a car like the S3 its worth it if max performance bothers you.

    In my experience I noticed very little difference because my journeys are short and I don't tend to push to the limit daily, or much at all.
    #62
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  23. Mdritchie
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    Mdritchie New Member

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    [Aug 7, 2014]
    Limited evidence, hence my cautious wording and absence of bold claims. I have re-read my comments and I think I was pretty clear about that. Limited evidence but I'm erring on the side of caution and the manufacturer's recommendation. I'm sorry if that aggravates you so. Until someone devises a set reproducible "real driving condition" tests I guess I will stick to my £170 p.a. fuel supplement and not worry too much about it.
    #63
  24. cilurnum
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    [Aug 7, 2014]
    A little more about direct injection engines and their problems:

    Ask An Engineer: GDI Problems In A Nutshell | The Truth About Cars

    The amusing thing is that in all the recent debates about fuels and emissions modern petrol engines are more like diesels than traditional petrol engines and they produce rather a lot of nitrogen dioxide themselves. The fact is with many different types of journey cycles, and the short journeys people mistakenly say are better for petrols, you're not going to make up for that with any anti-knocking mechanism.

    In order to keep these engines running trouble-free you need to be using higher grade fuels and they need to be serviced regularly.
    #64
  25. Audimad
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    Audimad Active Member

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    [Aug 7, 2014]
    Not all of them.
    #65
  26. cuke2u
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    cuke2u Well-Known Member

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    [Aug 8, 2014]
    Yup five years, or many many debates on several forums and still nobody has reproduced any of the claims made by the oil companies that produce these products, so no proof exists what so ever. And seeing as direct injection has been around for years it is unsurprising that individual car manufacturers might have had design issues around their systems however that doesn't mean that all direct injection engines will suffer significant problems at all. If they were then Internet would be screaming it out.
    I also, in this world of, so called, austerity, prefer to use my £15 per month saved for something more useful than just putting into the pocket of some multi national company whose profits under this global recession, where I have to fight to keep my job through the totally unnecessary cuts this government has made, have actually gone up drastically.
    #66
  27. M1ke H
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    M1ke H Member

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    [Aug 8, 2014]
    To the point about manuals above, the fuel filler cap on my S3 reads:

    Unleaded fuel only RON/ROZ 98 Super Plus or min. RON/ROZ 95 Super, Premium

    I haven't checked the printed manual, but the electronic version I have reads thus:

    Unleaded fuel only RON/ROZ 98 Super Plus or min. RON/ROZ 95 Super, Premium

    The use of Super Plus petrol (98 RON) is recommended. If that type of fuel is not available, premium petrol (RON 95) can be used with with a slight loss of power.

    If premium petrol is not available, the engine can be run on regular petrol with 91 RON as an emergency measure. In this case only use moderate engine speeds and a light throttle. Fill up with premium or Super Plus petrol as soon as possible.​


    There is also a series of notes including:

    • High engine speed and full throttle can damage the engine when using petrol with an octane rating lower than the correct grade for the engine.
    #67
  28. cilurnum
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    [Aug 10, 2014]
    Yep, that's the text that I'm referring to and there's no real room for misinterpretation there even though they've obviously had to word carefully.

    The internet is screaming about direct injection engines (and to be fair it's not just a VAG problem), but of course, not everyone will encounter problems all at the same time. Once you get one of these engines though, the clock is ticking, particularly if you think you'll save money on fuel versus a diesel or you actually want to try and get out the 140HP these engines allegedly have. The underpowered 122 engines are even worse. You will end up with a bill for a new engine at some point and beware second hand ones.

    These engines are less like traditional petrol engines and more like diesels in order to drag out the fuel economy versus power petrol now has to compete with, and petrol technology really isn't designed to do that.
    #68
  29. cuke2u
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    cuke2u Well-Known Member

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    [Aug 10, 2014]
    I think that is scaremongering, you do not know for sure this will happen at all and what you are stating is pure supposition. GDI do used diesel technology for sure but they do not run like a diesel....
    #69
  30. terapati
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    terapati New Member

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    [Aug 10, 2014]
    Any suggestion guys?
    #70
  31. cilurnum
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    [Aug 10, 2014]
    It's not scaremongering at all and people need to be aware of how to look after these engines and what might be on the horizon. You only need to look at the manual guidelines VAG are giving above and ask why they are doing that. I do know this will happen sooner or later because these engines have been discussed at length in VAG forums and elsewhere over the past few years. Technology has certainly got better but there is one immovable obstacle in getting these engines to work as reliably as traditional engines and that's the fuel itself.

    Diesel engines have certainly had their problems over the years, and the biggest problem with a diesel is the difficulty in getting the fuel to ignite reliably which is why compression and direct injection is used. However, it does mean that once ignition is achieved the fuel is a lot more controllable and less volatile. The opposite is true of petrol engines. It's easier to ignite owing to its increased volatility, which traditionally means you don't need all that complex and expensive compression equipment, but of course, the fuel doesn't burn as thoroughly. This means you need bigger capacity engines to get more power (especially at low RPM) and the economy isn't as good. Enter direct injection.

    DI engines take a volatile fuel in petrol and then adds compression into the mix to get more power at lower displacements and get the fuel to burn more thoroughly, increasing power and economy - and emissions. The problem is that you're introducing two unstable elements - more compression with a more volatile fuel. This obviously means that controlling unwanted explosions, or knocking, is absolutely vital. Technology and engine management systems are important but they can only do so much. The biggest unstable element here is the fuel and its tendency towards volatility and knocking. Then you throw a turbocharger in there. That isn't going to go away until petrol's refining process changes and effectively a new fuel is developed to take into account this process. That will, of course, be expensive and any excuse will be used to make it so. Diesel is a natural lubricant where petrol simply isn't.

    Petrol technology is at a crossroads in its development in that engines are getting ever more complex to keep up with the demands of economy and power but the fuel is more difficult to control than diesel under those constraints. I await with trepidation what problems will occur with the new 'cylinder on demand' engine because effectively you're placing all the load and stress on two cylinders rather than four. As technology has to improve to make this work reliably you'll end up with an engine just as expensive as a diesel running on a more expensive fuel.
    Last edited: Aug 10, 2014
    #71
  32. cilurnum
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    [Aug 10, 2014]
    I think there's enough information here for you to decide not to do it unless you can get 98 RON. If not you're going to end up with a pretty hefty bill out there somewhere.
    #72
  33. terapati
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    terapati New Member

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    [Aug 11, 2014]
    Thanks for reply. What's the worst scenario?
    #73

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