Thin oil myths and usage on old engines

I've been wondering about oil viscocity in engines and myths surrounding them. I've heard many times from random users that thin oil is bad for engines, it will destroy your cylinder walls etc etc and that you should rather use manufacturer specified viscosity or thicker oil if your car is burning oil.

But none of them could back up their claims, it was all just he said she said bullshit. Does anyone have actual data of what would happen if I would use 0w-20 on an older engine, for example Honda B series?

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  1. 7 days ago
    Anonymous

    there is nothing wrong with using thin oil provided your oil temps stay around 220-230F during operation
    it becomes a problem when you are hitting high oil temp (260F+) under extreme load, for example when driving aggressively on a track

  2. 7 days ago
    Anonymous

    oil flow through an engine is designed around oil pressure from the oil pump. low viscosity oil will not harm your engine if its designed for it. using a different viscosity can damage your engine. using a lower viscosity can cause lower oil pressure. using higher viscosity doesn't create higher oil pressure, it creates flow restrictions which can cause low oil pressure in the parts of the engine that arent worn out. so it might quiet that noisy part of your engine but its fricking the rest of the engine.

  3. 7 days ago
    Anonymous

    >waaaaa waaaa I'm a fricking moron and I can't do my own research please spoonfeed me
    this topic has been well researched and documented

  4. 7 days ago
    Anonymous

    in moron terms youre trying to make pasta sauce with tomato juice instead of tomato paste, youre gonna grenade your engine

  5. 7 days ago
    Anonymous

    Thin oil is bad. You want the oil stick a littlebit on parts. Lubricate your door hinge with wd40 and next mont it squeeks again. Lubricate it with a proper grease and it is good for years

  6. 7 days ago
    Anonymous

    > I would use 0w-20 on an older engine, for example Honda B series
    Don't be tempted. I put mobile 1 0w30 in my trail blazer during winter time and oil pressure would drop to 0 during hard driving, I changed it pretty quickly, but the damage was done. and the engine burned out at 260k miles which was only 20k after I tried that

    • 6 days ago
      Anonymous

      The first number has absolutely no meaning when the engine is at operating temperature. A 5w30 and a straight 30 have the same viscosity when the engine is at ~200F. The difference is that the 5w30 will start flowing and lubricating sooner after a cold start. Also 0w and 5w are actually the same viscosity for some reason.

  7. 7 days ago
    Anonymous

    well the 0w is the winter weight, itll warm up and get to 20 very soon

  8. 7 days ago
    Anonymous

    Watch project farm on YouTube.

  9. 7 days ago
    Anonymous

    I'm going to be real I buy 15w40 buy the barrel and I just put that in everything I own. Hasn't caused a problem yet AFAIK.

  10. 7 days ago
    Anonymous

    >if your car is burning oil

    It's too late, the damage has already been done. Thicker oil is to prevent that from happening. To have it happen is the result of using thinner oil, or aged and unchanged oil that don't have the viscosity they once had. The fact is thinner oil in modern engines with higher running temperatures is not good for them. They only do it to pass the EPA when tested, and that's why it's in the owner's and service manual. That don't matter if you don't plan to keep because it's the same as not changing the oil at all.

  11. 7 days ago
    Anonymous

    >that you should rather use manufacturer specified viscosity or thicker oil if your car is burning oil
    Honestly I just dump in whatever oil I can get if I can't find what is recommended. If it pours like 5W-20 cold, I'm fine with it going into the engine.

  12. 7 days ago
    Anonymous

    >Honda B-Series
    I have a B18A1. I use Rotella T6 5w40. In the winter, if you can source it, I recommend Rotella T6 0w40, but 5w40 will be fine too.
    They also make T6 10w30 now, also a good option for the B-Series.
    Don't use 0w20 in that engine.

  13. 7 days ago
    Anonymous

    >I've heard many times from random users that thin oil is bad for engines
    Not an issue if your engine is designed for it(truly), and you don't live in "extreme heat" or run your engine like a raped ape.

    The reason you should do research is what is your engine REALLY designed for. Many other countries that don't have cafe/epa/carb bullshit run thicker oil in those engines. This is because they don't have to meet the same MPG ratings and the engine was actually designed for thicker oil.
    Most modern engines aren't like this, but many in the 2000's-2010 were.

    Over here in my area we are having 2 weeks of 100F+ weather. When I owned a 5.4 3v they originally came with a 5w-30 recommendation, but that changed to a 5w-20. Well I said sod off and went with a 10w-30 since it had 220k miles on it and the timing chain rattle was real on hot days.
    Less chain rattle, engine was smoother, and since 40F is the absolute coldest it gets here it worked great.
    TLDR learn about your engine first before you mess with weights. If it's high mileage and hot where you live you can try thicker. If it's cold where you are don't go thicker on the Winter grade.

    Oh, and the bigger the spread in oil winter-normal ratings like 5w-50 the more VII's you have that can shear down, and make the oil thinner in usage. This is bad in the summer.

    • 7 days ago
      Anonymous

      >Oh, and the bigger the spread in oil winter-normal ratings like 5w-50 the more VII's you have that can shear down, and make the oil thinner in usage.
      Change your oil, homosexual.

    • 6 days ago
      Anonymous

      >Many other countries that don't have cafe/epa/carb bullshit run thicker oil in those engines.
      ex. Honda K24A4 beater engine runs 5W20 to pass emissions/fuel economy standards, while the near-identical K24A2 "sports sedan" engine runs 5W30. Identical crankshafts, near-identical blocks, most parts are interchangible. Same engine, different oil.

  14. 6 days ago
    Anonymous

    (OP)
    >I've been wondering about oil viscocity in engines
    As long as there is sufficient new oil flowing into the bearing raceways and other frictional surfaces, there will be oil preventing direct metal contact. The advantage of higher viscosity oil is that it is slower to be squeezed out from between two frictional surfaces than is thin oil especially in NON-IDEAL situations.

    If operational conditions are always ideal, then any reasonable viscosity is acceptable. However, if non-ideal situations occur such as excessive load or stress, then it is better to have more viscosity between the two surfaces unders stress. Notably, with thin oil, there is statistically greater chance that two frictional surfaces can contact each other. The tolerances for operation with thin oil also need to be tighter, thus there is less leeway for wear to occur because that wear basically eliminated the tight tolerances. So, that in turn accelerates wear. That doesn't mean the engine has shorter lifespan since many people are willing to keep using a car that vibrates more or has a loud clattering valvetrain.

    However, one cannot simply use 5W-30 oil with an engine designed with tolerances for 0W-16 oil. That's because valve timing at higher operational speeds are based upon thinner oil that flows away faster. Thus the thicker oil can cause slight shifts in timing. So, even if bearing wear qualifies a shift away from 0W-16 to 0W-20 and then 0W-30, the valve timing does not. These contradictory conditions also explain my some people say you should switch to thicker oil over time and why others say you should not switch but use the recommended oil viscosity. There is no single answer that is correct for all situations due to this. Of course, under ideal conditions for a NEW engine, the 0W-16 is the correct choice for NEW non-worn engines designed for that oil.

  15. 6 days ago
    Anonymous

    [...]

    very interesting point about valve timing, thanks for the info

  16. 6 days ago
    Anonymous

    >Does anyone have actual data of what would happen if I would use 0w-20 on an older engine, for example Honda B series?
    That takes hundreds of thousands of dollars of research. Are you asking if anyone here did it ourselves or if we googled it better than you and were able to come up with different results?

    The difference between 0W-20 and 5W-30 is likely less than the difference in viscosity any one oil experiences throughout its wear cycle and temperature range. I don't think it's a big deal. A lot of owners manuals give oil grade charts to tell you what to use for various ambient temperature ranges, and usually there's a lot of overlap where you could use a variety of viscosities.

    I do know of engines where the manufacturer spec was 5W-30 in the earlier years and 0W-20 in the later years. Toyota 2GR-FE for example. I can only speculate on the reason for the change. Is it to get better MPG from less oil pumping losses, or is the thinner oil actually better for the engine? Did they update any of the engine parts to adjust for the change in oil? You can dig through parts diagrams between 2006 and 2016 to see what changed because I don't care enough to.

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