7.5 interval oil change
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This is a discussion on 7.5 interval oil change within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; The manual says to change the oil every 7.5k. Yet i hear that everyone does theirs every 3k. Im torn ...

  1. #1
    Registered User teck7droid's Avatar
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    7.5 interval oil change

    The manual says to change the oil every 7.5k. Yet i hear that everyone does theirs every 3k. Im torn apart on what to do. Do i really need to be spending extra money? Or should i follow what the manual says. Well, i drive my car easy, rarely racing the engine. id say about 90% of my shifts are below 3k rpm.
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    Brian Trinidad

    Pearl Black 03 Wrx, 5spd, turbo gauge, Spoiler, Progress lowering springs Cusco front and rear sway bars, Gutted uppipe, helix v2 dp, greddy evo catback!

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    He simply abides. SD_GR's Avatar
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    Change your oil at 3K like the manual says. Then change at 6k, and at 9k, 12K. Now you can chose your favourite oil. Do lots of research and no matter what get an API SL oil and save all your receipts for US warranty purposes, no matter what any salesperson says. In general oil company "guarantees" are as worthwhile as me promising you a check in the mail (you pick an amount or I'll leave it blank...), so don't waste your time if it's not an API SL oil.

    (I say this b/c some rather upscale firms in the US "don't bother" to API cert their oils, and say "if you have a problem and it's oil related we'll back you up" but it's nearly impossible -- not a chance, forget it, etc. -- to prove a failure is due to oil legally.)

    Now, after your initial manual-dictated drains, you have some choices. Pull your air filter and eyeball it. If it's filthy at 11K or so, you live in a dusty climate. No ultra-long oil drain intervals and no intakes/CAIs/ram air/aftermarket air filter rubbish either (these are a dodgy idea for *anyone* and in a demanding climate only the works filtration system will do - dirty air accelerates motor wear dramatically).

    Consider your oil consumption, if any, over your 11k, and consider the climate you'll be seeing over the next interval. Check the manual and pick the right viscosity - I use 10W-30 M1 in SoCal myself. Tastes vary.

    Anyway, having done all that, drop in your favourite oil, and go another 3K to 15k total on the odometre. Do all the silly stuff at the 15k service, and now use the same oil, and stretch to 4K miles. (This ought to be OK considering the manual says 3750-7500 for dino oil 5W-30 API SL, and that accounts for all the mediocre oils out there too). Pull a sample and send it to a lab for analysis. The results will be data, not enthusiast-style "hot air" or opinions, and you will know for a fact whether the oil is holding up to that drain interval. The lab may say "go more, it's OK" or they may say "change." Even if they say go more, I'd change anyway, then go more the *next* interval - you will be in the 20s by now.

    You may in fact find that you can safely stretch your change interval to 7500; I've no idea nor does anyone else, so you have to get data. Factors that'll affect the max drain possible are the oil you use, the way you drive, and where you drive.

    You may also find that you need to top up to the extent that you are actually replenishing the oil's additive package, effectively "stretching" the oil's life. Or that you need to swap a filter every half drain interval, top up, and go the rest. Only the analysis will show.

    If all this sounds too involved, just drain at 3K or go to 3750 after the second change like the manual says and call it a day. Either way will work.

    Have fun!
    SD
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    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
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    Registered User teck7droid's Avatar
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    Thank you for the 411, I live in so cal also los angeles county. Where can i send in the oil for testing? I did my first oil change at 3k like the manual said. Im at 6.5k right now, according the manual the next oil change is it 7.5k,15k,22.5k... Reading the sticky about periodic maintanence, at the top it a chart give the oil change intervals at 7.5, then another chart says every 3.75 can you please give me more information to clear up my misunderstanding? I really appreciate everyones help PS ill be sure to get the approved oil with guarantee !
    Your Pal,
    Brian Trinidad

    Pearl Black 03 Wrx, 5spd, turbo gauge, Spoiler, Progress lowering springs Cusco front and rear sway bars, Gutted uppipe, helix v2 dp, greddy evo catback!

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    He simply abides. SD_GR's Avatar
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    This link lists two different places to get oil analysis done - just be sure to stick with whichever lab you pick, or your results may not be consistent over time and may not provide as good a comparison as possible:

    http://www.bobistheoilguy.com/oilanalysis.html

    The 3750 mi interval is for severe use. In your area heavy traffic might result in extended idle periods, for example, which effectively shortens the drain interval - although you are not moving, the oil is still working, so the actual miles it'll last are less. Other problems might be short trips - the oil never reaches decent temp and the volatiles that need to be evaporated off are retained, increasing their concentratio - fuel is an example of this. Or towing, extreme hot or cold (desert or Greenland etc.).

    Although you cannot go wrong changing at 3750, you may not need to. Again, only analysis will show... Analysis will cost as much as a full oil change, so run the math before doing this routinely - if you are changing at 3K, for example, analysis will only tell you what oil works best for your car but it will still be a long process (don't analyze the first drain of an oil you've switched to; analyse the second) and at the end of the day, almost any over-the-counter oil will get you to 3K in relative safety, so it may not be worth it to you. But if you want to find out what an oil will do for you as far as extening the drain to the max allowed (NO MORE for the warranty period) then analysis is the answer - plus, the data is a great document to have in your car's service record should anything arise, I suppose (no personal experience there).

    Incidentally, go to the home page at the site I linked you to and jump around the dicsussion boards there; it's a *VERY* informative site and you will quickly learn more than you ever wanted to know about lubrication. Plus, they have a spreadsheet of SUBARU-specific oil analysis data, which is great! Overall a fantastic resource. Once you pick an oil you might like, go to the site and look it up and see what results others have gotten with it - I love this, because it takes marketing and old wive's tales out out of the equation completely.

    No offense to marketers or old wives, but these two factors IMO are responsible for most debates and wasted time/money/effort.

    My car got dino juice every 3k mi from the dealer until 12 k, then got M1 10W-30. I'll be checking use, if any, and seeing if I can go 5K or so on this. I keep all my receipts, and I use works filters though you can go anywhere and get a Purolator that differs only in the paint scheme. I also get a new drain plug crush washer - good form, I suppose.

    Off Topic: Say, "neighbour," you wouldn't happen to know an excellent detail shop, would you? OC or SB counties?
    Last edited by SD_GR; 05-26-2003 at 10:43 AM.
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    Wow man, that's a lot of reading, so I didn't read it. haha. Here's my view on it. I change my oil at max every 3k miles. I do run my engine hard. I rarely see noticably dirty oil when I drain it. Look at your oil when you drain it, if it's a good color then you're good. If it's really dark, and esp. if it's not runny, then you need to change it sooner. That's about the jist of it. All you have to do to keep your warenty is change it every 7.5k if that's what the book says. I've never looked in the thing because the only time my cars seen the dealership was when I left after I bought it.

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    Administrator Trainrex's Avatar
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    I have a friend Who has always religiously changed his oil on All his cars every 7500. Ive seen many of his cars last hundreds of thousands of miles (he owns a limo fleet) I just can't seem to get myself to do it. That oil starts creeping over 3000 and I start gettin nervous. I like to think better safe than sorry, especially if you plan on keeping your car for a while.

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    He simply abides. SD_GR's Avatar
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    Tribology vs. Psychology = Drain Interval?

    Originally posted by trainrex
    I have a friend Who has always religiously changed his oil on All his cars every 7500. .... That oil starts creeping over 3000 and I start gettin nervous. I like to think better safe than sorry, especially if you plan on keeping your car for a while.
    It's propaganda!

    A long time ago the oil would have to be drained and warmed outside the motor before starting.

    By the time Laurel & Hardy hit the cinemas one had a fighting chance of starting a car without removing and warming the oil.

    By the 50s one could actually go a couple thousand miles on the same oil. People were amazed.

    By the 70s, despite an oil crisis or two, the oil companies had begun a massive campaign to get people changing oil every 3K mi or 5K Km in Europe and the Americas. Given the state of their products back then I can't fault them for that.

    But attitudes changed and the products changed too. The original M1 was seal-unfriendly and very thin (20 weight!) but it's gotten *tremendously* better since then. And consumers almost everywhere *except* the US decided changing the oil on prompt like Pavlov's dogs was really not on - no reason to and a complete hassle that tossed out expensive (elsewhere certainly) and precious resources.

    So today we have specs like "BMW Long Life" or Merc's 229 series - the latest 229.5 says oils must:
    - Start life as an ACEA A3-02 (Only a handful of oils available OTC in the US can dream of this, and it gets tougher still!)
    - Protect as well as 229.3 BUT increase fuel economy by 1.8 % (If memory serves...)
    - Protect for something like 18,000 miles!
    Clearly an oil meeting MBZ 229.5 has no relation to 5W-30 dino juice that many a Subie dealer has cheerfully put into a WRX.

    But for 3K mi intervals, *either* will do just fine IMO. So you could keep the car running indefinitely with almost the worst oils on the market, following a religious drain interval schedule that's short enough. No problem. It might be cheaper too.

    But if you want to stretch the drain to the max allowed, gain fuel economy, and/or get the max protection possible, a more evolved oil might be a better bet.

    The easiest way to break the 3k habit is to get hard data on an oil's performance. Do analysis, there can be no questio then.

    Or just forget about it and do 3k changes and live life happily - I admit I tend to get a little goofy about all this tribology stuff, and it may be a character flaw of mine...

    Cheers,
    SD
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

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