Viewing 17 posts - 41 through 57 (of 57 total)
  • Posh petrol maths help
  • 5lab
    Full Member

    cos your driving style has differed? because you’ve done different driving? because you’re filling the neck of the fuel tank as well as the tank? because traffic is lighter? because the weather is better? because its warmer?

    there’s nothing, at all, in science that could make your car more efficient with 98ron fuel. you may as well wear a bracelet with a magnet in

    molgrips
    Free Member

    bog standard cars are *very* unlikely to see any benefit from 98 ron car to start with.

    That’s what I thought originally but someone else said otherwise up there ^^^

    FeeFoo
    Free Member

    cos your driving style has differed? because you’ve done different driving? because you’re filling the neck of the fuel tank as well as the tank? because traffic is lighter? because the weather is better? because its warmer?

    there’s nothing, at all, in science that could make your car more efficient with 98ron fuel. you may as well wear a bracelet with a magnet in

    I hear what you’re saying and I’m sure you’ve got your petrochemical/combustion science correct.
    However, as I said above, my commute has not changed in traffic density, distance or route. I don’t use the car at the weekends, we use another one.

    I drove for 6 months on 95 ron and now 10 months on 98 ron. The mileage I’m getting is different.

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    gonefishin
    Free Member

    there’s nothing, at all, in science that could make your car more efficient with 98ron fuel. you may as well wear a bracelet with a magnet in

    Well that’t not strictly true though is it. By retarding pre detonation it ensures that a higher proportion of the fuel injected is burned at the correct time within the 4 stroke cycle, thereby increasing the amount of useful energy extracted. It is also a fairly simple thing to test as all you would need is an engine on a test bed to eliminate all other variables.

    allthepies
    Free Member

    gonefishin +1 – engine management systems are designed to cope with fairly poor grade fuels, if you can guarantee higher fuel quality then the engine management system can tweak the variables available to it in order to make the process more efficient.

    br
    Free Member

    The modern world.

    The poster can afford a flash car but can’t work out the fuel consumption… no wonder the UK is going to the dogs.

    clubber
    Free Member

    Yeah, it’s political correctness gone mad, isn’t it 🙄

    Wally
    Full Member

    My pub explanation.
    “It’s simple – Petrol is mainly a mixture of Heptane and Octane, with 7 and 8 carbon chains. The longer the chain the higher the chemical stored energy – more bonds to break requiring energy but considerably more energy released when these rebond with oxygen – exothermic. RON rating (research octane number) indicates the ratio of Heptane to Octane, higher the RON the higher the ratio of longer chain Octane in the fuel so more vvrooom. Mines a Mahito please.”

    molgrips
    Free Member

    I drove for 6 months on 95 ron and now 10 months on 98 ron. The mileage I’m getting is different

    That’s enough for seasonal factors to come into play. Petrol engines are more efficient when the air’s warm because it’s less dense and you need less fuel for stoichiometric ratio. You’ll see less power at max throttle, but more economy at normal cruising speeds.

    Gonefishin – sounds reasonable, I wonder if the 5th gear test was invalid because the cars didn’t have any time to adapt their maps to the new fuel..? And IIRC that was quite a while ago wasn’t it?

    stgeorge
    Full Member

    I drove for 6 months on 95 ron and now 10 months on 98 ron. The mileage I’m getting is different

    Perhaps the engine is now run in…….

    Switch back to 95 ron for a few months and see if mileage reverts to old figure.

    gonefishin
    Free Member

    I don’t remember the 5th gear test but I do remember one on the Gadget Show that did show a difference, but to be honest I’m not sure that I’d trust either of those shows. All I’ve pointed out is a possible mechanism as to why there may be improved performance/economy, it doesn’t necessarily mean that there is one. Also, whether or not it is economic to use the more expensive fuel is another question entirely.

    ftr1873
    Free Member

    I seem to find that V-Power does provide better economy compared to standard fuel. I know the fuel light isn’t the most scientific method but from full to light V-Power gives a consistent 30 miles extra, which I reckon easily offsets the extra cost of the fuel.

    5lab
    Full Member

    even BP only claim that you get an average improvement of 13 miles extra per tank, which they put down to lubricating components in the fuel, as well as cleaning elements. Assuming a 600 mile tank (bp are unlikely to have tested this on a small car), that’s an improvement of 2% – so in mpg terms – assuming 35mpg, it’d be approx 0.6mpg improvement

    http://www.bp.com/sectiongenericarticle.do?categoryId=9018273&contentId=7033278

    I expect if some cars magically did an extra 5mpg, bp, shell et al would probably be advertising the fact

    molgrips
    Free Member

    How many petrol cars do 600 miles on a tank?

    More likely 400 miles which makes it a massive 3% improvement.. 🙂

    Still on the Prius that could mean an extra 2mpg if you are lucky.

    FunkyDunc
    Free Member

    Do people really get improved performance on 98 ron? IMO its more placebo in terms of acceleration. However it definately makes engines smoother and tends to get more mpg if driven sensibly.

    5thElefant
    Free Member

    Do people really get improved performance on 98 ron? IMO its more placebo in terms of acceleration.

    Should do. See the knock sensor conversation above.

    Doesn’t apply to older cars and even relatively new motorcycles though.

    FeeFoo
    Free Member

    Perhaps the engine is now run in…….

    Switch back to 95 ron for a few months and see if mileage reverts to old figure.

    Well, the car had 55K on the clock when I got it and now it has 72K. I reckon that’s run in enough.

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