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Thread: Does RON number impact fuel efficiency?

  1. #41

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by yanyewkay View Post
    Esso
    I swear by Esso because they used to have good CC offer (3% off) and with my dividend CC i get some cash back after that.. so makes it worth while for me. The petrol is also quite 'powerful' engine reponds well.

    Shell
    I hate Shell because of stupid rules they implemented that pissed me off (nothing to do with the petrol quality ) Petrol quality feels quite good actually. I was really able to get more milage out of their petrol during their campaign that time.

    SPC
    I have no idea, but SPC seem to feel the weakest of all the petrol company, i have to step harder and the engine is slow to respond. It feels like my tyres were deflated to 50%

    Caltex
    Caltex is about the same as SPC but give slightly more power than SPC (feels like a 20% deflated tyre? )

    Just my personal preference. SPC has the more confusing rebate schemes.

    Anyway, the shell "water" is it because some old man looked at the Shell advert which shows some island and water around and so he said, "Shell gets their fuel from the sea! it must contain water!!"
    Hmmm.. Then I will try Esso and Shell to see which one give me a better $$ economy. Thanks for the heads up.

  2. #42

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by yanyewkay View Post
    steam engine will be the power myth i heard about someone developed a way to pump water into the tank of a conventional car and runs off water.. ultimate!!
    I thinkn can pump hydrogen in.. but water......... hmmm.... Cold fusion engine? Or like Back To The Future, the car which runs on trash?

  3. #43

    Default Re: Does RON number impact fuel efficiency?

    to straighten things up abit here.

    The correct terms to use for knocking is uncontrolled detonation. Commonly termed as knocking or pinging. During a uncontrolled detonation in 4 stroke cycle, the fuel self-combust (ie detonated) during the compression cycle before the sparking of the plug. This uncontrolled detonation created tremendous amount of pressure within the cylinder and creates shock wave which will resonate and becomes a knocking sound.

    The detonation is a result of compression rather than the commonly believe hot piston.

    In a 4 cylinder car, such detonation occurs during compression cycle, the piston is moving upwards and compressing but the detonation has already occurred so it is fighting the compression action of the piston. The stress here is tremendous.

    In order to curb this uncontrolled detonation, tetra-ethyl lead was used. The RON rating, as many has pointed out, is the ability of the fuel to withstand compression.

    Modern car engines are equipped with knock sensors and will automatically retard engine timing to prevent engine 'knocking'. However, the retard in timing is at the expense of peak efficiency for the engine. Therefore, RON does affect engine power output especially under load (ie uphill).

    As for fuel economy, the lower RON will only improve carburettor engine. For modern fuel injected engine, the ECU is able to run at optimum air to fuel ratio via the O2 sensors.

    So why still pump lower RON petrol? Because the difference in power output for RON 98 and RON 95 and RON 92 is negligible for family sedan cars but the price difference is HUGE! And thus the savings in $$$.

    As for blowing engine on performance cars using low RON petrol, is because the ECU can only retard the engine timing to a certain level, especially so for forced inducted engines whereby the air is much hotter and in much higher pressure when entering the cylinder.
    Last edited by chisiang; 21st January 2008 at 07:05 PM.

  4. #44

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by chisiang View Post
    Modern car engines are equipped with knock sensors and will automatically retard engine timing to prevent engine 'knocking'. However, the retard in timing is at the expense of peak efficiency for the engine. Therefore, RON does affect engine power output especially under load (ie uphill).

    As for fuel economy, the lower RON will only improve carburettor engine. For modern fuel injected engine, the ECU is able to run at optimum air to fuel ratio via the O2 sensors.

    So why still pump lower RON petrol? Because the difference in power output for RON 98 and RON 95 and RON 92 is negligible for family sedan cars but the price difference is HUGE! And thus the savings in $$$.
    Thanks for the explanation! So RON does impact efficiency... Which means there should be an optimum RON for each car, right?

    I just pumped my 3rd 3/4 tank of RON92 petrol today and it does seem like my FC is taking a slow plunge from 14km/l down to 13km/l. I think I will go back to RON95 for my next few top up to see if I can get back 14km/l. That does translate into $0.14/km(RON95) vs $0.15/km(RON92).... I need more statistics but I'm impatient..
    Last edited by lsisaxon; 22nd January 2008 at 09:35 AM.

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