Regular Oil, Mix, or Full Synthetic
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This is a discussion on Regular Oil, Mix, or Full Synthetic within the STi Engine Performance forums, part of the STi Technical Forum category; Dealer said when i got that car that "subaru's don't like synthetic" is this true or if it is that ...

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    Registered User S4toSTI's Avatar
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    Regular Oil, Mix, or Full Synthetic

    Dealer said when i got that car that "subaru's don't like synthetic" is this true or if it is that kind of synthetic do all you use such as 0W40 or 10W40 and so on TIA.
    -Barry

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    Moderator YBNormal07's Avatar
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    Many use synthetic with no issues at all. I use mobile 1 and never a problem.
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    Registered User j69raw's Avatar
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    Can anyone tell me if it is OK to use 10W30 Full synthetic on my 2005 STi?

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    He simply abides. SD_GR's Avatar
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    Can anyone tell me if it is OK to use 10W30 Full synthetic on my 2005 STi?
    Your manual can. Inside there is an oil chart that shows what viscosities are appropriate for certain temperature ranges and use conditions. In general, if you are in GA and it doesn't get ridiculously cold (Greenland comes to mind...) a 10W-30 ought to be an acceptable viscosity.

    Search for my data using a 5W-40 Mobil1 in my 2.0L for 5,800 miles. I switched to that from 10W-30 mainly because I think the 5W-40 M1 is a bargain at the price it's selling for, and also to see if I could reduce my motor's oil use.

    Definitely have a look at the oil sticky threads in the mainenance forum. Pages and pages of user comments and more information than anyone could hope to provide by individually responding to your question. Good stuff.
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    Registered User kool168's Avatar
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    Quote Originally Posted by j69raw
    Can anyone tell me if it is OK to use 10W30 Full synthetic on my 2005 STi?
    of coz you can..

    i also heard someone saying that they switched to mobile 1 0W40 and it yields better gasmilage.

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    Registered User j69raw's Avatar
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    Quote Originally Posted by SD_GR
    Your manual can. Inside there is an oil chart that shows what viscosities are appropriate for certain temperature ranges and use conditions. In general, if you are in GA and it doesn't get ridiculously cold (Greenland comes to mind...) a 10W-30 ought to be an acceptable viscosity.

    Search for my data using a 5W-40 Mobil1 in my 2.0L for 5,800 miles. I switched to that from 10W-30 mainly because I think the 5W-40 M1 is a bargain at the price it's selling for, and also to see if I could reduce my motor's oil use.

    Definitely have a look at the oil sticky threads in the mainenance forum. Pages and pages of user comments and more information than anyone could hope to provide by individually responding to your question. Good stuff.
    Cool, because I have 3 cases in my garage!

    Thanks!

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    He simply abides. SD_GR's Avatar
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    Buy new oil because you need dated receipts to show when you did the oil changes. You can always keep your existing stash for when warranty issues are long gone (60,001 miles).
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    Not to hijack this thread BUT....I am looking to switch to synthetic with 24k on the odometer. I have read posts from a few people while searching this topic that it is a bad idea to switch to syn after using std oil because of seals that tend to shrink when used with syn.

    Is this true? I have been using a synthetic blend for the last 15k so maybe it wouldn't be as bad but I just didnt want any problems with burning oil.

    Can any one offer some input here?

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    Moderator YBNormal07's Avatar
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    Quote Originally Posted by VOLFAN
    Not to hijack this thread BUT....I am looking to switch to synthetic with 24k on the odometer. I have read posts from a few people while searching this topic that it is a bad idea to switch to syn after using std oil because of seals that tend to shrink when used with syn.

    Is this true? I have been using a synthetic blend for the last 15k so maybe it wouldn't be as bad but I just didnt want any problems with burning oil.

    Can any one offer some input here?
    Ummm..since this is the topic of discussion, it's not a hijack. I'm not sure what you are asking since it's already been said the synth. is ok for our vehicles????
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    Yes, I know syn is OK for our cars but I have read in several threads concerns over switching to synthetic after using dino oil for so long. Some have said that the seals/rings shrink with synthetic oil use so you get more oil usage/burnoff. My main concern in switching to 100% syn at 24k miles was that I would start seeing excessive oil usage when I have had none before.

    I plowed through several pages during my search however and found my answer....guess I will be switching to synthetic tomorrow and feel better after reading some more on it.

    Thanks!

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    I'll chime in here. I don't know that anything really shrinks so much as it just has an easier time getting through small passages, i.e. small leaks turn into moderate leaks.

    Now as for why you might WANT to use a synth check this.

    http://www.lubricantsuniversity.com/...=94&Itemid=105

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    Another tidbit

    http://www.machinedesign.com/ASP/str...tedArticle.asp

    Look for the table at the end if you want a summary. Note that Mobil 1 is basically a PAO.

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    He simply abides. SD_GR's Avatar
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    Quote Originally Posted by VOLFAN
    Not to hijack this thread BUT....I am looking to switch to synthetic with 24k on the odometer. I have read posts from a few people while searching this topic that it is a bad idea to switch to syn after using std oil because of seals that tend to shrink when used with syn.

    Is this true? I have been using a synthetic blend for the last 15k so maybe it wouldn't be as bad but I just didnt want any problems with burning oil.

    Can any one offer some input here?
    Modern seals and modern synthetic oils are inherently compatible. The agents in modern synth oils that would tend to cause seal swelling are counteracted in proper oil formulations by agents that counter that effect. To make a long story short, no, the oil is not harming your seals.

    That's not to say switching to a synthetic won't cause leaks.

    A motor that has seen lots of miles with a conventional oil and high temps, extended drain intervals, poor filtration, or all of these together will have deposits and junk. What this does is two things: first, it prevents oil from reaching the seals as it sticks to them instead. Oil is designed to condition seals. When they get blocked off by junk, they dry up and disform. This would normally cause a leak. However, the same junk just bakes on and temporarily hides that leak point.

    Now, along comes a good synth oil with excellent detergent properties. All that junk hiding the failed, dried up seal and the subsequent leak is slowly solubilized and/or just plain knocked loose, ending up in the filter. Now the leak is evident...

    24K miles on a modern API SL oil of the correct viscosity and using the correct drain intervals is not a tremendous mileage though. The seals in such a motor should be in quite good shape, and I'd consider a switch to synth myself. Your mileage may vary of course, and all this is IMO.

    As for the possibility of increased useage, I'd expect it at least for the first 5K miles, maybe a bit more. Eventually though the motor will settle down to its normal useage pattern with that particular oil. If that particular useage pattern, once it's set in, is still unacceptable to you, try another oil and give that one 5K or more miles before concluding as well.
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    Thanks for all the help!

    Put my mind at ease.

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    Registered User Silver04Sti's Avatar
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    Quote Originally Posted by S4toSTI
    Dealer said when i got that car that "subaru's don't like synthetic" is this true or if it is that kind of synthetic do all you use such as 0W40 or 10W40 and so on TIA.
    -Barry
    I've run Amsoil 5w30 synthetic on all my cars including my sti and never had an issue with any of them including:


    >120K on my old civic si
    >90K on my old maxima se
    >36K on my old modded wrx
    approaching 30K on my sti

    Granted, I don't run it to 25K change intervals like they advertise but I do run them 5-7K between changes and have never had an issue. I actually have a buddy who ran it to 20-25k in his expedition and did several oil analyses along the way and they always came back clean. He's just braver than I am!
    Volvo S60 R (as of July 05)

    Formerly ka: BlackWrx
    SOLD 7/05----04 Silver STI
    SOLD: 02 black sedan, Lots of mods

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