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Thread: Does RON number impact fuel efficiency?

  1. #21
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    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by gooseberry View Post
    Basically the RON or octane rating gives you an indication of the amount the fuel can be compressed before it spontaneously ignites - the lower the RON, the less compression it can take. Igniting from compression causes engine knocking - which can be quite bad for the engine.

    One of the ways of increasing engine power (while keeping engine volume the same) is to increase the compression ratio of the engine - doing so means that you have to use a higher RON fuel to avoid knocking. So generally more powerful engines of the same volume need a higher RON fuel.

    There doesn't seem to be any evidence that using a higher RON than what your engine was designed for gives you any added benefits that outway the extra cost.
    interesting..i always tot, the RON value is oni an indication number that tells whether the petrol is more environmental friendly or not..
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  2. #22
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    Default Re: Does RON number impact fuel efficiency?

    higher more friendly? or lower more friendly?
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  3. #23

    Default Re: Does RON number impact fuel efficiency?

    friendly on wallet or car?

  4. #24

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by yanyewkay View Post
    higher more friendly? or lower more friendly?
    From web sources, lower is more friendly because the higher ones tends to add benzene, a potential carcinogen, to increase the anti-knocking capability.

  5. #25

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by tan131 View Post
    Adding onto what gooseberry has said, ron is onli impt to ur car if ur car's ECU is programed to o/p the bhp/torque using the particular fuel. Meaning, traditionally high compression engines ie 10.5:1 or honda/suzuki 11.0:1 requires high octane petrol to prevent pinging or early detonation. Hence the higher the compression, the higher the oactane u may need. NA racing cars even require octane booster as they run insane levels of compression. The worse i knoe of, was a b18c type R which blew even running on v-power. The compression was above 12.5+:1.

    However, if u take a look at force induction engines, they may require high octane petrol despite their low compression. This is because some force induction engines are tuned to o/p power/torque @ a particular octane rating. This is why like megaweb mentioned, top gear's test showed the WRX to o/p the highest figures @ the highest octane petrol.

    This is also why japanese cars have two different models. JDM & export. Japan has one of the highest octance petrol available to consumers. Whereas the export models factor into consideration of the mass market out their. This is also why some of their performance breeds especially the WRX & type R, there's a difference between the JDM & export models in performance figures. They are tuned for different octane petrol.

    So conclusion is.. most of our cars do not need high octane petrol. For fuel economy, it may be due to easier combustion of low octance petrol (i'm not too sure abt this). As for performance, there is no difference unless ur ECU is tuned to perform at high octane petrol or u are driving a car with high compression engine. Any differences felt are usually in our mind unless its proven :P

    Dun forget, there are countries still running on ron 87, 91, & 95 being their highest.
    My Latio 1.5 engine has a compression ratio of 10.5:1, which is considered quite high when I compared it to other engines. Vios is comparable. But yet RON>91 is specified, so it means that it should not knock with RON92 petrol, right? ECU is also able to detect knock and back off the petrol if necessary. How does this impact performance? Doesn't it mean that we will not be able to whether the RON is suitable because we cannot feel the engine knocking? What also puzzles me is that some other engines do not specify such a great compression ratio but requires a higher RON to prevent knocking..

    87 is usually AKI (anti-knock index) number which is equivalent to about RON91-92. AKI numbers are lower than RON from what I gather over the resources over the web. So the numbers you presented may be AKI equivalents to RON 92, 95 and 98 respectively. I think US is using AKI numbers instead of RON (research octane numbers).

    Esso and shell websites mentioned that if the car can take a lower RON petrol, a higher RON petrol will not give a better performance. Cleaning additives are also supposed to be the same across the board, so there should be no advantage of using a higher RON number unless the engine manufacturer specifies it. But people here always say higher number better.. Is it because of the "$$ more=better" mentality?
    Last edited by lsisaxon; 21st January 2008 at 04:01 PM.

  6. #26

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by gooseberry View Post
    Basically the RON or octane rating gives you an indication of the amount the fuel can be compressed before it spontaneously ignites - the lower the RON, the less compression it can take. Igniting from compression causes engine knocking - which can be quite bad for the engine.

    One of the ways of increasing engine power (while keeping engine volume the same) is to increase the compression ratio of the engine - doing so means that you have to use a higher RON fuel to avoid knocking. So generally more powerful engines of the same volume need a higher RON fuel.

    There doesn't seem to be any evidence that using a higher RON than what your engine was designed for gives you any added benefits that outway the extra cost.
    Yeah.. if it combusts before the cylinder completes the compression stroke, the explosion would be opposing the direction of the engine's rotation.

    What I'd like to know is whether using a lower RON petrol (as low as the engine can take) would give an FC advantage (cost comes later). If there is no difference, then the cost part is also an advantage.

  7. #27

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by lsisaxon View Post
    My Latio 1.5 engine has a compression ratio of 10.5:1, which is considered quite high when I compared it to other engines. Vios is comparable. But yet RON>91 is specified, so it means that it should not knock with RON92 petrol, right? ECU is also able to detect knock and back off the petrol if necessary. How does this impact performance? Doesn't it mean that we will not be able to whether the RON is suitable because we cannot feel the engine knocking? What also puzzles me is that some other engines do not specify such a great compression ratio but requires a higher RON to prevent knocking..

    87 is usually AKI (anti-knock index) number which is equivalent to about RON91-92. AKI numbers are lower than RON from what I gather over the resources over the web. So the numbers you presented may be AKI equivalents to RON 92, 95 and 98 respectively. I think US is using AKI numbers instead of RON (research octane numbers).

    Esso and shell websites mentioned that if the car can take a lower RON petrol, a higher RON petrol will not give a better performance. Cleaning additives are also supposed to be the same across the board, so there should be no advantage of using a higher RON number unless the engine manufacturer specifies it. But people here always say higher number better.. Is it because of the "$$ more=better" mentality?

    Pardon me, I think high compression shld probably fall in closer to the region of 11.0:1 (edited mys post)

    To answer your question, engine compression is only one factor thing. The other factor would be the program on ur ECU and how it was tuned. If your manufacturer recommends ron 91, it is most likely tat though ur engine runs on a higher compression then others, the ECU is tuned for ron 91 petrol. The combination of engine compression and ECU map will determine the rating of petrol to be used.

    As for the other manufacturers recommendations, it could be because though it has a lower compression ratio, the figures given by the manufacturer is based on the ECU tuned to that of a higher ron rating. Doesn't mean that if the owner were to use a lower ron petrol, it wld give knocking. Perhaps, he/she will not be able to acheive manufacturers claims.

    Well, it could be a different index. But in most places, ron 95 is the most commonly available grade. 97 & above is rather rare. This could be a reason as to why the discontinued Honda integra type R that ships to australia is detuned (ie. ECU is set to a lower ron rating) as compared to the JDM model.\

    Lastly, the websites are right. If ur ECU is tuned to a say ron 91 and u obtain a particular o/p, using ron 95 will not give u a higher set of figures. That is unless u remap the ecu

  8. #28

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by tan131 View Post
    Pardon me, I think high compression shld probably fall in closer to the region of 11.0:1 (edited mys post)

    To answer your question, engine compression is only one factor thing. The other factor would be the program on ur ECU and how it was tuned. If your manufacturer recommends ron 91, it is most likely tat though ur engine runs on a higher compression then others, the ECU is tuned for ron 91 petrol. The combination of engine compression and ECU map will determine the rating of petrol to be used.

    As for the other manufacturers recommendations, it could be because though it has a lower compression ratio, the figures given by the manufacturer is based on the ECU tuned to that of a higher ron rating. Doesn't mean that if the owner were to use a lower ron petrol, it wld give knocking. Perhaps, he/she will not be able to acheive manufacturers claims.

    Well, it could be a different index. But in most places, ron 95 is the most commonly available grade. 97 & above is rather rare. This could be a reason as to why the discontinued Honda integra type R that ships to australia is detuned (ie. ECU is set to a lower ron rating) as compared to the JDM model.\

    Lastly, the websites are right. If ur ECU is tuned to a say ron 91 and u obtain a particular o/p, using ron 95 will not give u a higher set of figures. That is unless u remap the ecu
    Ah! Now that's clearer. So for those lower compression engines which specifies higher RON numbers, it's more of a performance tuning issue rather than a knocking issue? But shouldn't they be able to obtain the performance using a lower RON petrol? Also, these cars with low compression seems to poor FC performers also. Do you think it's a case of tuning optimization and these engines actually have the potential to perform better on FC as well as power?

    So far, I see that the engine compression ratio of cars with good FC, eg Latio, Jazz, City i-DSI, Vios, all have a compression ratio of about 10.5:1 (Jazz is 10.4:1, City i-VTEC is 10.1:1). Is this the optimum?

    So I guess using RON92 for these engines (I think all of them specified RON>91) would give the best bang (pun intended) for the buck?
    Last edited by lsisaxon; 21st January 2008 at 04:29 PM.

  9. #29
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    Default Re: Does RON number impact fuel efficiency?

    time to hoot RON95...
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  10. #30

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by Del_CtrlnoAlt View Post
    time to hoot RON95...
    You using RON98 now? Let me know your FC after you change to RON95. I dunno if my FC is better or worse after I changed to RON92 from RON95 because my route changed also..

    But I think for the same RON, the brand does matter, doesn't it?
    Last edited by lsisaxon; 21st January 2008 at 04:55 PM.

  11. #31
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    Default Re: Does RON number impact fuel efficiency?

    so far after 10 years of driving... i never for once monitor my FC...
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  12. #32
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    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by Del_CtrlnoAlt View Post
    so far after 10 years of driving... i never for once monitor my FC...
    Rich!!!
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  13. #33
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    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by lsisaxon View Post
    You using RON98 now? Let me know your FC after you change to RON95. I dunno if my FC is better or worse after I changed to RON92 from RON95 because my route changed also..

    But I think for the same RON, the brand does matter, doesn't it?
    it does, diff brands have different additives.
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  14. #34

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by Del_CtrlnoAlt View Post
    so far after 10 years of driving... i never for once monitor my FC...
    Oh okie.. Maybe I'm a bit obsessed about FC.. hahaha.. Maybe just let me know if you feel that you're visiting the pump less often or more often..

  15. #35

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by yanyewkay View Post
    it does, diff brands have different additives.
    Which do you think is better? Some people swear by Esso, some Shell. Not many like Caltex and many say avoid SPC? I'm using up my SPC vouchers quite soon, so it's about time for me to change..
    Last edited by lsisaxon; 21st January 2008 at 05:11 PM.

  16. #36
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    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by lsisaxon View Post
    Which do you think is better? Some people swear by Esso, some Shell. Not many like Caltex and many say avoid SPC? I'm using up my SPC vouchers quite soon, so it's about time for me to change..
    there use to be a myth abt shell petrols got "water"...is this myth still goin on?
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  17. #37

    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by blazer_workz View Post
    there use to be a myth abt shell petrols got "water"...is this myth still goin on?
    Hmmm... will it improve FC? Steam engine?

  18. #38
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    Default Re: Does RON number impact fuel efficiency?

    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!!"
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  19. #39
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    Default Re: Does RON number impact fuel efficiency?

    Quote Originally Posted by lsisaxon View Post
    Hmmm... will it improve FC? Steam engine?
    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!!
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  20. #40
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    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!!
    pump in is easy... any tom dick and harry can do it...

    but running it...
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