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  1. #1
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    Synthetic Oil Question(s)

    First some background. My dad has a 2000 Nissan Xterra, the first generation of them with the 6 cylinder engine and a 5 speed manual transmission. My dad has never been one to maintain his cars, he buys it and drives them till they stop running, yet still seems to have exceptional luck with them. Case in point, our Xterra has almost 92,000 miles on it, and he's changed the oil a grand total of 4 or 5 times. Despite that being the only maintainence EVER done to the car other than new brake pads at 70,000 miles, the car runs fantastically.

    However, I'm worried that going so long between oil changes is bad for the engine, and since I recently got my license, I'm pretty fond of driving this car and want it to last. So heres the question. We've always run conventional oil in, at the recommened 5W-30 viscosity, but I've been thinking about putting the higher mileage rated Mobil1 synethic stuff in it when I change it next. We talked to the guy at the autoparts store about this, and he claimed that you could not switch to synethic oil after 6 years of running conventional oil because the seals would leak.

    That sounds like bullshit to me, but because I didn't wanna fuck anything up, we went with normal oil(around 20,000 miles ago). But lately, I've been thinking about it, and was wondering if this could work. Since it calls for 5W-30 conventional oil, would using 10W-30 synethic oil reduce any chance of seals leaking? Since synthetic viscosity is not temperature sensitive, I assume you could run thicker oil no problem, and the high mileage additives to synthetics make them appealing.

    So, maggot collective, whats the word on synthetics vs. conventional oil?

  2. #2
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    Read this site until your brain feels like a left testicle


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  3. #3
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    The only reason the seals might leak is from the cleaning properties of the synthetic oil. The first couple of oil changes with syn will be pretty dark because it will be slowly cleaning all the carbon/varnish residue from running dino without frequent oil changes.There is no reason to switch unless you are looking to run higher milage oil change intervals.Just run a good dino with a decent filter and call it good.It would be wise to run Auto RX through your engine to clean out all the crap from those extremely long OCI`s your dad was running.I`m running 16 k intervals with delvac 1 and oil testing at the lab to go along with it.Do a search on it at the BITOG site.

  4. #4
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    wow, and I feel dirty and wrong if I go 3500 miles instead of 3000.

  5. #5
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    heh, my dad would NEVER change the oil in his cars, just add more if it occurred to him and it didn't occur to him very often. I remember one time (actually it was the last time) he started it and flames shot out of the exhaust at least 15 feet, like a rocket. Still he drove almost 1000 miles a week and routinely kept cars until they had over 200K on them. Really not sure how he managed it.

  6. #6
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    "It is not the result that counts! It is not the result but the spirit! Not what - but how. Not what has been attained - but at what price.
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  7. #7
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    That is what happened to us when we bougth a older car and started treating it right. Didn't even put in syn just started changing oil more freq. and gaskets started to leak. If you don't change oil gunk coats gaskets on inside so outer portion of gasket dryies out. Remove gunk , oil leaks through dried out gasket.
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  8. #8
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    I think the proper interval is somewhere between ice's dad and Yeti. So, between 5k and 100k miles.

  9. #9
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    Running synthetic oil and the good filter as opposed to the cheap one will allow you to go longer between oil changes without incurring damage. You should pour a can of Sea Foam into your crank case to clean out the sludge and deposits you have almost certainly built up by not changing the oil. If your seals begin to leak after cleaning the internals and running a smoother flowing oil, use an oil stabilizer like Lucas Oil Stabilizer to prevent or slow leaks. If I had the choice between leaky seals or a gummed up engine, I'd take the leaky seals every time. Leaky seals are treatable, but if your oil tracks get gummed up, you're eventually going to do serious damage to your valve train.
    "I smell varmint puntang."

  10. #10
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    There was a dude here in town that bought a brand new Ford Explorer and took it home. He NEVER did a thing to it, including an oil change. He brought it up to the dealership (I worked there for about 6 weeks in college) when I was working there with 40,000 miles on it and the engine had seized. He wanted all his money back, because he said he was told it was maintenance free to 100,000 miles.
    "Have fun, get a flyrod, and give the worm dunkers the finger when you start double hauling." ~Lumpy

  11. #11
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    That's bull. You can switch to synthetic oil whenever you want.
    Oil decays over time. Synthetic oil simply has a better "behavior" than conventional, i.e., it responds/flows better for longer periods.
    For change intervals however you should always stick with what the owner's manual recommends. That's your golden standard.

    On top of that, you may have some variability depending on your circumstances...


    From Roadologist Ultimate Guide to Motor Oil:
    Generally speaking,
    - if your vehicle is new, or
    - if your driving mainly consists of sessions of 20 minutes or more at fairly steady speeds (as opposed to stop-and-go traffic)
    then you can probably increase a bit the mileage between oil changes without consequences.


    Instead,
    - if your vehicle has more than a couple of years, or
    - if your driving mostly consists of shorter than 20 minutes sessions or of stop-and-go traffic, or
    - if you frequently drive off-road or in particularly dusty/sandy environments
    then you should definitely consider decreasing the time between oil changes, and perform more frequent maintenance (e.g., every 3000 or even 1000 miles).

  12. #12
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    I’ve really softened my stance on this over the years.

    The 75,000 mile change interval I experienced driving for Schneider National was part of it.

    At this point I’m doing Mobile 1 for the non-leaker-burners and heavy diesel oil for my loose old 351M.

    Changes in the spring and fall, regardless of mileage.

  13. #13
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    Strange bump...

    I originally didn’t realize this was an old thread and was more interested that the OP had been posting since 2003 but just recently got his license m than the state of the vehicle.

    Out of curiosity, how did it turn out OP?


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  14. #14
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    Quote Originally Posted by shafty85 View Post
    Strange bump...

    I originally didn’t realize this was an old thread and was more interested that the OP had been posting since 2003 but just recently got his license m than the state of the vehicle.

    Out of curiosity, how did it turn out OP?


    Sent from my iPhone using TGR Forums
    I think I ended up running Mobil1 High Mileage 10W-30 in it, and drove that thing until it had around 140,000 miles on it. It never burned or used oil. I traded it in for a Subaru that I couldn't say the same for.

  15. #15
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    I've heard that thing about not running synthetic in a well used engine but I have no experiance with it

    I ran specail 505 spec (or whatever ) synthetic that was 10$ a litre in a VW TDi that was mandatory in those engines, it would use a litre every 4000 kms which wasnt so bad

    the ultimate in lowtech super cheap to own V6 ranger took cheap 10-30 or whatver the dealer put in it and it burned nothing in over 100,000 kms
    Last edited by XXX-er; 08-17-2020 at 08:20 AM.
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  16. #16
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    Yeah, out of the three vehicles I've owned, the Outback was by far the most comfortable on long road trips, but it used 1-1.5 quarts of oil every 5,000 miles from the day it was brand new.

    That being said, I drove that thing in Michigan and Utah for it's whole life, and when I traded it in, there was not a spot of rust anywhere on the vehicle. My 4runner was rustier when I drove it off the lot with 4.5 miles on the odometer. If they had produced the Outback with the 3.6 H6 engine and the 6 speed manual gearbox that mine had, I would still be driving one. That would have been a pretty close to ideal vehicle for my needs/usage.

  17. #17
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    Don't over analyze motor oil. Use the grade recommended in your owners manual. No scientific evidence that your engine will last longer using synthetic oil. Both conventional and synthetic oils are API SN+ rated. For most drivers you can change your oil twice a year and stay within the manufactures recommendation. If your vehicle has an oil life monitor pay attention to it. It uses a complex algorithm taking in account your driving style, miles, temp, trip length, engine rpm's etc. I have a Ford Explorer that 80% of the miles are long trips on the interstate with almost no stop and go driving. The OLM would have me go over 10,000 miles between changes. I do changes twice a year deal and use full synthetic as it is not that much more expensive when on sale. In fact if you shop Costco they sell Kirkland full synthetic made by Warren Petroleum. Two five quart bottles for $29.99, $3 quart. It does meet GM's Dexos requirement.

    If you want to know more, way more than you need to know go to "Bob Is the Oil Guy".

  18. #18
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    the best oil in the world isn't going to make up for shit filtration (air and oil).

  19. #19
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    cover

    Quote Originally Posted by I Skied Bandini Mountain View Post
    the best oil in the world isn't going to make up for shit filtration (air and oil).
    Premium filters such as Fram Ultra, Wix XP will go longer. High quality air filters keep your oil cleaner. Don’t let the service guy tell you a new air filter will give you better gas mileage, it will not.

  20. #20
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    Just change that shit regularly with OEM parts and stop fretting over it.

  21. #21
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    Quote Originally Posted by glademaster View Post
    Just change that shit regularly with OEM parts and stop fretting over it.
    My point exactly

  22. #22
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    Quote Originally Posted by bigdude2468 View Post
    Premium filters such as Fram Ultra, Wix XP will go longer. High quality air filters keep your oil cleaner. Don’t let the service guy tell you a new air filter will give you better gas mileage, it will not.
    I mean, in theory it could, but only if things are really bad to begin with.

    My experience has been that OEM oil filters are a better bet than aftermarket, as relief valving tends to be unknown in the aftermarket filters; YMMV.

    My experience with a Nissan Xterra, on the other hand, was that getting a full service done (engine, transmission and diff fluids; plugs and wires; timing belt; etc) didn't help much, as it still seized four thousand miles later (albeit with 227k on it).

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