Mixing auto trans fluids
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  1. #1
    1000+ Posts Haakon's Avatar
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    Mixing auto trans fluids

    Had the trans serviced on the R21 (AR4 4sp auto, same as an R19 AD4). I assumed that they would have put in synthetic oil. When I asked, they said no because it is not good to mix with the Dextron 3 (as on only gets about half the fluid out in an oil change). Rememebered later that the last bloke who serviced it put in synthetic.
    So I now have either half/half synthetic/dexron, or one quarter synthetic, depnding on what was in it before last time.
    What should it have in it, and is it a big deal to mix and match fluids?

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  2. #2
    Good Sport danielsydney's Avatar
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    Haakon I would not have thought it would have made any difference as long as it is high quality. 2_cents

  3. #3
    Budding Architect ???? pugrambo's Avatar
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    the thing is with ATF is that different oils react differently at different temps also different oils will have different amounts of additives that they use and they work out how much the average tranny needs and put the amount of additives needed so now with yours you will not have the amount of additives that the oil manufacturer has worked out is a good thing in your tranny
    it shouldn't be any cause for concern but you can if you like over time replace the oil with whatever oil you wish to have in the tranny
    in regards to not bieng able to completely drain the tranny is true to a certain degree but you will find that most of the oil will drain out
    the only oil that will stay in the tranny during a change is the residual that remains in various valves and galleries as such through out the hydraulic system in the tranny
    this is fairly minimal though and not really a great concern
    as for compatabilty yes he is right to a certain degree but for the amount that would be mixing isn't enough to worry about
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  4. #4
    1000+ Posts Haakon's Avatar
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    apparently the torque converter holds as much oil (which cannot be drained) as the rest of trans.
    This wouldnt be such a problem if these trans had a drain plug and a dipstick......
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  5. #5
    Fellow Frogger!
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    Hi, last time i replied to a post about oil and identifying myself as a lubrication specialist i was shot down by all these poeple who PM me and asked all these really difficult and stupid questions, of which i replied with correct answers, and they all hid back in the woodwork, i would like them to stay there with this post..
    This is my opinion only;
    As a general rule of thumb, it is a big no no to mix mineral based oil/Greases together with synthetics.
    Sometimes i found that nothing out of the ordinary happened, but sometimes, when you mixed synthetic greases they went runny, and the bearings failed. (Grease is just a thickened version of Oil.)
    Mixing trans fluid's may cause the trans to slip, the oil may start foaming (Which is common when you mix mineral oils and synthetic oils), if left may severly damage you trans.
    Trans fluids are a tough one because you can only drain out half the oil becaues of the torque converter.
    I beleive you shouldn't even mix different brand mineral oils, as each brand of oil is made up of different components, such as different viscosity modifiers, different anti foaming agents, different wear reducing addatives.
    When you mix oils all these packages mix together and sometimes the chemicals used in one brand, can mix with the other brand and cause a chemical reaction.
    Foaming of the oil, is the usual result, WHICH IS VERY BAD!!!, sometimes it can even come out of the dipstick hole.
    I'm not a mechanic but if there is a way you can empty the torque converter and use only one oil the better it will be i think.
    Oh and one other thing check your manufactures specs on what type of trans flud you should use, don't just put any trans fluid in, as they are not "All the same" as some people think.
    There's my 2_cents
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    Adrian Colman
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  6. #6
    1000+ Posts Haakon's Avatar
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    and my friends ask my why I work on my cars all the time - its because I am yet to have a satisfactory experience from someone else doing it. At least if I stuff it up there is noone to blame.

    My Haynes manual says "Dexron type ATF" is the juice for the AR4 - is dexron 111 or synthetic any diferent/better/worse?
    It also says I get 4 out of 5.7 litres out at renewal.
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  7. #7
    1000+ Posts Haakon's Avatar
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    just a thought - what about all the semi synthetic engine oils on the market (I use the shell one in the R25 - I got .5 litre/100km improvement in economy) - arnt they just a mix of sythetic and mineral oils?
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  8. #8
    Fellow Frogger!
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    Dexron, type III is the current standard, excellent whilst the new Dexron type IV will be suitable for colder temperature starts, with tighter tolerances.
    Differences between dexron II, and Dexron III is the higher temperature stability found in Dexron III, and the new auto's are running hotter, and hotter.
    I have found Redline High temperature Synthetic, which meets the dexron III standard an excellent product, so too the Lubrication Engineers 1107 ATF Fluid.
    And if you can afford it the Redline synthetic D4 has an excellent Viscosity Index, and will work well in high stress applications according to thier specs:
    <a href="http://www.redlineoil.com/redlineoil/atfpds.pdf" target="_blank">Redline ATF Synthetic Specs</a>
    It must also be noted that synthetic trans fluid and gearbox oil is not like synthetic engine oil, that may breakdown in normal service, synthetic trans fluid and gear oil isn't subjected to the various fuel deposits and acids that combustion engine oils are subjected too.

    Semi- Synthetic engine oils, are made up of about 75% mineral base stock, and about 25% synthetic base stock, that is compatible with mineral oils, the additive package however is the mineral oil package not the high performance package found in some synthetics. Then it is all blended together, i wouldn't reccomend just mixing synthetic with mineral based. buy a semi synthetic already blended proffesionally, with the correct additive %'s
    So in a nutshell, you will get better performance out of semi synthetic oil than mineral oil, and you shouldn't have too many problems with the oil breaking down before your next service interval because it is 75% mineral oil which makes is more reliable.
    Well this is only my opinion..
    Cheers
    Adrian Colman
    Peugeot
    "Anything else is a Compromise!"

  9. #9
    Budding Architect ???? pugrambo's Avatar
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    Haakon:
    apparently the torque converter holds as much oil (which cannot be drained) as the rest of trans.
    This wouldnt be such a problem if these trans had a drain plug and a dipstick......
    these are a sealed unit are they not ?????
    they are totally separate from the tranny
    if you have a torque coverter out of a car you turn the filler hole to 2 o'clock to fill them up

    synthetic trans fluid and gear oil isn't subjected to the various fuel deposits and acids that combustion engine oils are subjected too.
    and hence oil turns black over time in an engine
    3 x '78 604 SL

    1 x '98 306 GTi6

    1 x secret project

    1 x '98 406 STDT troop carrier and i don't care if it stinks, i don't sniff it's arse Death by wank tank

    1 x '99 406SV 5spd wagon, time to burn more fuel

    1 x 1994 605 SV3.0


    WTD long range fuel tank for 605

  10. #10
    1000+ Posts Haakon's Avatar
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    nothing about the AR4 is sealed, but the diff runs its own seperate oil (renault say its sealed but it has drain and level plugs and got refilled with fresh sythetic diff oil last service) from the rest of the trans, but the torque converter is supplied with pressurised fluid from the trans.
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