306 and 91RON unleaded
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  1. #1
    Tadpole
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    Default 306 and 91RON unleaded

    This kinda relates to this earlier thread:
    306 (XSi) ECU re-mapping for 92 RON

    When I got my '94 306 I was told by the previous owner that the dealer who sold it to her told her to run it on regular unleaded (91 RON) and she has never had any problems with this.

    I'm thinking that perhaps, given that back in 1994 there was no premium unleaded available in country Victoria, maybe the dealership reprogrammed the ECU to run on 91RON instead of 95RON as specified all over the car.

    Do you think this is likely? Or do you think that engine is just more tolerant of regular unleaded than the newer ones?

    If it was retuned by the dealer, do you think there would be any benefit in getting it tuned back to its factory setting to take advantage of 95RON (premium)? There's no problem finding premium unleaded nowadays.

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    '94 306 XR

  2. #2
    Moderator Alan S's Avatar
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    I don't think there is any way to switch from one to the other, this is the job of the ECU that is governed by sensors.
    At that age, I would suspect it would have been fitted with a knock sensor and this is what up to a point controls the spark by retarding/advancing when a "knock" or ping is detected.
    I've found on a lot of cars of that era, changing from ULP to PULP is more a matter of psychosematics or people believing their cars are going better on the PULP than they did on the ULP.
    The only cars they seem to have an effect on are the ones with the higher compression ratios and on some of the earlier carby cars that were high compression and designed for high octane fuels which used to be "Super" that morphed into "Leaded" that became "LRP" and is of a lower octane rating than the original stuff they were designed for.
    These older types which have a manually adjustable timing, can be advanced to take advantage of the higher octane. This doesn't necessarily mean that a lower compression engine will get anywhere near the same effect as most of the old High Comp carby/distributor cars have had their timing retarded to allow for the lower octane LRP they were conned into using.


    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  3. #3
    Tadpole
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    Quote Originally Posted by Alan S
    I don't think there is any way to switch from one to the other, this is the job of the ECU that is governed by sensors.
    At that age, I would suspect it would have been fitted with a knock sensor and this is what up to a point controls the spark by retarding/advancing when a "knock" or ping is detected.
    I've found on a lot of cars of that era, changing from ULP to PULP is more a matter of psychosematics or people believing their cars are going better on the PULP than they did on the ULP.
    The only cars they seem to have an effect on are the ones with the higher compression ratios and on some of the earlier carby cars that were high compression and designed for high octane fuels which used to be "Super" that morphed into "Leaded" that became "LRP" and is of a lower octane rating than the original stuff they were designed for.
    Hi Alan,
    Thanks but I'm not quite sure that I understand fully. Maybe I should explain better.

    The handbook for the car, as well as stickers in various locations of the car, state quite clearly that the car must be run on 95 RON fuel, however the previous owner and the dealer she bought it from said to run it on regular, which is 91 RON. The engine is electronic injected, compression ratio is 9.25:1, it's 8 valve. The handbook says that the engine must be run on 95RON but it mentions in passing that it can be tuned by the dealer to allow it to run in 91 RON. That is what I want more information about. How likely is this to have been done and should I continue to run it on 91RON as assured by the previous owner or should I run it on 95RON as specified on the car? I don't know whether to trust the previous owner more or the handbook and stickers on the car, and whether any work has been carried out to adjust the car to run on 91RON.

    Maybe this is a question for a Peugeot dealer.
    '94 306 XR

  4. #4
    Moderator Alan S's Avatar
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    Matt,

    I would just go with the 95 RON if that's the case. You can bet pennies to peanuts the dealer won't have done anything to it (regardless of what he might say). I doubt there's too many dealers in Oz that concientious (or capable).

    Usually you have a fair bit of leeway on this as it's not like the leaded/unleaded issue where hardened valve seats and all that kind of thing comes into calculations.


    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  5. #5
    Fellow Frogger! Decca's Avatar
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    Matt Ray, I seem to recall when I got my 405 the dealer said it will run on ULP or PULP but It is certainly a nicer car on the PULP as the engine is more tractable, doesn't pink (rattle) when under power at low revs and... I get much better fuel economy. Extra cost of PULP is negated by extra tank range.

    I have been told that PULP will keep the injectors clean. Mine have never been cleaned , now has 195000 on clock.

    Drive on a tankful of each fuel and compare


    Decca
    Present --2016 2008 Outdoor / 2014 RAV4 Diesel (My utilitarian beast)

    Past -- 19?? 403 / 1974 504GL / 1972 R12TL / 1995 405SRi / 1997 406ST / 1998 306XT / 2004 406HD1 / 2008 308XSE HDi / 2008 307XSE

  6. #6
    Tadpole
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    Thanks for your help! I'll keep with the PULP then.
    '94 306 XR

  7. #7
    sans witticism SLC206's Avatar
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    Quote Originally Posted by Matt Ray
    Thanks for your help! I'll keep with the PULP then.
    When I got my 306 XT back in 1995 (with the same mighty 1.8l 8v XU9 I think), I remember the manual said quite clearly that it runs on 95 (and in fact there was a sticker on the fuel filler that slapped you in the face when you opened it and told you not to use anything else,

    however

    The manual also said quite clearly that if it was inconvenient (ie. living out in the boonies in 1995), your dealer could "adjust" the car so that it would run ok on 91.

    I wouldn't use 91 unless you could be sure this "adjustment" had in fact taken place, and in any case you will probably get more mileage out of PULP anyway.

    Incidentally my 306 pinged like a trooper every day of its life, despite being run on 95 RON fuel, until I started using Optimax when it became available. It stopped pinging after that and I got an extra 50-100km out of a tank as well.

    The extra cost at the time (nowhere near the 10c litre extra that the burglars are charging for now) and the extra range from a tank of it more than made up for it.
    Regards,

    Simon

    2018 308 GTi 2011 DS3 DSport
    ----
    2014 208 GTi 2007 207 GTi 2004 206 GTi180 2000 206 GTi 1995 306 XT

    www.peugeotclub.asn.au

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