Much better oil pressure after oil change.

Discussion in 'Engine & Drivetrain' started by OneofFew, May 18, 2019.

  1. adriver

    adriver Full Access Member

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    MY owner's manual for (my 02 Silverado with a 4.8L/ LR4) tells me that the oil I should be using is 5W-30, and that 10w-30 is an acceptable backup. I notice a difference in the two. I notice a seat of the pants in difference in response (manual transmission, so yes I can notice it), and the 10W-30 maintains a more steady pressure, but its a little lower (around 60). The 5w-30 goes near 75 when cold, drops to about 50 at idle, and 65-70 when driving or getting on it. (I AM JUST GUESSING WHEN I SAY: ) to me, that seems like the 10w-30 is too thick, and only flowing as well as the pump is able to.

    I'm not going to tell you which oil to use, but if I had to choose between going off of a random suggestion online that tells you to guess at it, or going off your owners manual..... Go read your manual..
     
  2. BG1988

    BG1988 Full Access Member

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    been using 5w30 mobil1 75PSI cold start

    normals out to 55PSI idle..


    you have been using 6qts correct?
     
  3. MrBiggs228

    MrBiggs228 TYF Newbie

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    Had this same issue but with a low mileage 04. End up being the motor was so neglected that oil and sludge were caked up
    [​IMG][​IMG]

    End up putting a rebuilt motor in[​IMG]
     
  4. OneofFew

    OneofFew Full Access Member

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    Of course.
     
  5. OneofFew

    OneofFew Full Access Member

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    As to possibly using a higher viscosity oil- OEMs like recommending the thinner oil to get the fuel economy at the cost of longevity. In this case with lifter tick already evident at startup and the known lifter issues on the 5.3s , It may not be a good idea to go to a higher viscosity.

    To all- I appreciate the great comments and suggestions
     
  6. SnowDrifter

    SnowDrifter Full Access Member

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    That's a pretty generous claim that a recommendation of lighter oils causes reduced engine longevity. I trust you have data or some sort of study we can reference?
     
  7. swathdiver

    swathdiver Full Access Member

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    It does reduce longevity especially when they are running higher temperatures too. Grumpy Bear over on the GM-Trucks forum has been studying and posting about this for years with the K2s. I'm sure Blackstone-Labs has plenty of data too.
     
  8. SnowDrifter

    SnowDrifter Full Access Member

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    Save me a search through the hivemind?
     
  9. swathdiver

    swathdiver Full Access Member

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  10. SnowDrifter

    SnowDrifter Full Access Member

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    I only lightly skimmed the thread

    But to be entirely honest I'm rather dissatisfied at both his testing methodology and conclusions. Though, as a disclaimer, I couldn't view the images he posted as I opted not to register an account for this one task. If he's posted any UOAs I'd like to review them.

    1. He seems to be trying quite hard to correlate oil temp with effectiveness. I would argue it's more of a result of flow rate within the system rather than internal friction. After all, when an engine is running, everything operates on a hydrodynamic film. The parts don't actually touch eachother. It's possible he's measuring pumping losses but without any data on wear rates, those datapoints are meaningless.

    2. OP ran out of the gate with a thinner oil than what the manufacturer suggested. Seems to contradict earlier points in this thread (the ones I challenged)

    3. His comment/concern about oil frothing at the end of the thread is, I think, presumptuous. Again, too much time staring at numbers and trying to make conclusions rather than taking some measurements and observing results. Can't say oil is frothing based on a 3psi pressure delta. Would need a sight glass. Could potentially measure it, at least while flowing, with some sort of light diffusion test.

    4. Oil film strength as a product as viscosity I think really undersells an interplay of multiple variables. We're not dealing with a static situation here. It's actively pumped and the oil film being replenished. Take it to the extreme of too thick and you won't have the flow rate to appropriately replenish the cushion of oil by the time the crank swings back around. you could also run into cavitation issues which would eat a bearing very quickly.

    5. To be clear, my comment is on street vehicles. If you're racing, you should really know better than to run blind period. Everything will be determined per application. So don't go pulling up racing articles about oil viscosities showing wear rates. Those vehicles typically run a higher oil temp than you'd see during street use (duh) and actively need a thicker oil to compensate for temperature thinning. With that said, I maintain my point that MFRs aren't speccing thinner oil and seeing reduced engine life. I've yet to see any substantiating evidence that doing so reduces engine life. They're not going out and designing an engine then tossing whatever grade of oil in there is the thinnest they can get their hands on. Bearing tolerances, flow rate, bearing size (and by some extension bearing pressure/area) are all part of the design. If you do some poking on BITOG, a couple members have found benefit in running thinner oils in their engines, though once again, this is per application and the results determined through testing - it won't be indicative of every vehicle. Xw20 has been around now for over a decade. And while I hate to introduce personal experience as without documentation, it's more anecdotal than anything, I've seen dozens upon dozens of vehicles come in with 300k+ miles - taxi fleet stuff - that have been running the manufacturer recommended since day 1. Even had a couple 400k tahoes/yukons still ticking away on 5w30 - though one had some good rod knock. Always came in dipstick dry and overdue though, so no conclusion can be made here if an Xw40 would have been beneficial from a wear perspective (oil burning/leaking and owner negligence not withstanding)



    So I suppose the debate still stands. Need concrete evidence that manufacturers are recommending thinner oil, which then results in a lower engine life.

    Sorry OP for the thread hijack. If anyone's interested in continuing to discuss this, shoot me a note or we can make a new thread and continue jabbering there. I like our tech chats
     
    Larryjb likes this.

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