Chosen Oil Viscosity...?

Discussion in 'Gen 5 Prius Care, Maintenance and Troubleshooting' started by GuardianGrayHalcón, Dec 6, 2023.

  1. johnHRP

    johnHRP Active Member

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    HTHS makes a big difference in the main bearing wear. That's why GM revised back to 0w-40 instead of 0w20 on their pickup Trucks.
    Toyota engines are not known to have main bearing problems unlike BMW, VW, or GM.

    To compensate the thinner oil, most 0w-8 oil contains high amount of antiwear especially Borons. So, do not mess around with adding oil additives that mess the balance and optimum ratios of the additives and detergent.

    Toyota engine prones to piston rings clogging more. Viscousity Modifier (VM) % in 0w-40 or 0w-30 is higher than 0w20. VM tends to degrade faster and create deposit more.

    So choosing the oil viscousity depends where and how we use the car. Using 0w-30 or thicker is suitable in warmer climate or if we do towing or live in the mountains.
     
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  2. Hammersmith

    Hammersmith Senior Member

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    I'm just going to point out that GM's switch to 0W-40 is only because of the defective crank journals. If they had been machined properly, GM would never have switched to 0W-40 for those engines. If you have one of those engines and it's been damaged bad enough to warrant replacement, the new engine with a correct crankshaft will be specced right back to 0W-20.



    Personally, I have absolutely zero worries running 0W-16 in my gen5. I wouldn't have had any problems even if Toyota had specced 0W-8 like the same engine in the Corolla. As long as the engine is designed with the thin oil in mind, the engine parts are made of quality materials, and the manufacturing process means the finished product meets or exceeds the design specs, I'm fine. I don't know how confident I'd be with a GM, Ford, BMW, MB, or Audi that specced 0W-16 or 0W-8, but I don't worry about Toyota. I'll just do my 6m/5k mile changes and sleep well at night. The only thing I could wish different would be if Valvoline made Restore & Protect in 0W-16 and 0W-8.
     
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  3. Gokhan

    Gokhan Senior Member

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    Keep in mind that the antiwear/extreme pressure/friction modifier (AW/EP/FM) additives are for the valvetrain and cylinders, which do or may operate in the boundary-lubrication regime. For bearings, you need a minimum HTHS viscosity to achieve a minimum oil-film thickness (MOFT), as they operate in the hydrodynamic-lubrication region. For the boundary-lubrication region, both the base-oil viscosity and AW/EP/FM additives are important.

    Boron additives these days are almost always dispersants, not antiwear additives, even though a while back some oils experimented with boron antiwear additives. Toyota has been using a lot of boron dispersants in their genuine engine oils (TGMO) after its sludge problem. ExxonMobil makes the TGMO in the US.
     
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  4. Trollbait

    Trollbait It's a D&D thing

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    Is any non-Japanese brand recommending 0w16 or 0w8?
     
  5. Gokhan

    Gokhan Senior Member

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  6. Trollbait

    Trollbait It's a D&D thing

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  7. Gokhan

    Gokhan Senior Member

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    Just as ILSAC is a consortium of American and Japanese car OEMs, ACEA is a consortium of Euro car OEMs. ACEA did not have SAE 0W-20 until recently, but now, it is common with Euro OEMs. If SAE 0W-16 is in ACEA now, some Euro OEMs will adopt it in the near future, as ACEA is nothing but a governing body of Euro OEMs.
     
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  8. johnHRP

    johnHRP Active Member

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    That is right, some Ford engines consume oil if we use higher viscousity because the cylinder wall cross hatch patten is designed for thinner oil. I also prefer whatever recommended by manufacturer for most engines application. The only thing to prevent me using 0W-8 oil is pricing and aftermarket availability. If I can find it with reasonable price for newest Camry, Yaris, or Crown, 0W-8 is the one to go.

    I do not know if Toyota still have engines with chronic oil consumption problems like 2010-2014 Prius/PriusV/Corolla hybird engines. I found that thicker oil does not help on those engines. Only more frequent oil changes (5-8k miles) with high quality full synthetic oil helps. I think GTL Pennzoil, Shell, Quaker State Ultra Platinum helps because of more robust base stock that needs less additives to fullfill DexosD or Dexos1 gen3 requirement or higher.