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Terminology for fluids

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Frank O, Nov 28, 2014.

  1. Frank O

    Frank O Junior Member

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    I've been looking at the maintenance schedule for my 2011 Prius as well as Toyota's tech info site to prepare for doing the 40,000-mile maintenance items. They seem to use different terminology in different places, and I'd like to make sure my understanding is correct:

    -- The schedule calls for checking/adjusting "all fluid levels" every 5,000 miles. However, automatic transmission fluid and front differential oil are listed as separate items checked less frequently. So does the check of "all" fluid levels every 5,000 miles mean engine oil, coolant, brake fluid and washer fluid?

    -- In different places, Toyota refers to "engine/inverter coolant" or "engine/power control unit coolant." I assume the power control unit is the same as the inverter. And the engine and inverter use the same coolant, but they have two separate reservoirs?

    In addition, the following items aren't included at 40,000 miles, but I figure I ought to know about them for when the time comes:

    -- In different places, Toyota refers to "automatic transmission fluid" and "hybrid transaxle fluid." I assume these are the same thing, and there is only one place to check/fill it?

    -- I also see reference to "front differential oil," but haven't found a section in the tech info system on dealing with it. Is this different from transmission/transaxle fluid?
     
  2. css28

    css28 Senior Member

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    As far as I can tell, there is no separate differential oil or fluid--the transmission fluid is what does that. Unless there's evidence of external leakage its level souldn't need checking. I believe the only way to check it is by removing the fill plug and that's likely to introduce some dirt.

    The engine and inverter/power unit cooling systems are separate and need to be checked and changed independent ally (though they use the same coolant formulation).
     
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    The main fluids to check are the engine oil, the two coolant reservoirs and (wait for it) windshield washer fluid.

    do not know if it's just ours, but I've never seen the engine oil budge from the top mark where I set it at each oil change. And this is a first for me: with any previous car (all Honda) the oil level would drop about a pint, at least, between changes.

    At 48000 kms and 4 years both our coolant reservoirs are approaching the low line; I'm gonna stall till spring, then break down and get a bottle of the Toyota Spec'd premixed coolant, bring them up to the top line.

    Brake fluid level in the reservoir, I wouldn't touch. Unless there's some sort of disastrous fluid loss, it's perfectly normal for the level to drop as the brake pads wear. If you top it up as the level drops, it's just going to overflow when new pads are installed, and the pistons pushed back in to accommodate the thicker pads.

    Trannsaxle: again I'd just leave it alone. If you don't see any leakage, it's fine.
     
  4. Frank O

    Frank O Junior Member

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    Thanks. I too was impressed when I checked the engine oil and found the level very high. I'm used to engines that burn or leak a fair amount.
     
    #4 Frank O, Nov 28, 2014
    Last edited: Nov 28, 2014
  5. DoubleDAZ

    DoubleDAZ Senior Member

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    Wow! My experience has been just the opposite. I've owned 6 new cars (3 Ponchos, 1 Olds, 1 Chevy and 1 Dodge) and, yes, I used to do my own maintenance. To my knowledge, not one of them has ever budged from where I filled it after an oil change, not even the Montana with 166,000 miles on it. I have owned used cars that used some oil, especially my '63 Ford Galaxy.
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    By "very high" do you mean well above the full mark on the dipstick?

    I've done about 8 (DIY) oil changes now, and one thing I've learned: if you want the oil level to be at the top mark, put in the spec'd qty, and yeah, check the dipstick, but mainly just to verify the oil's somewhere between the marks, not seriously low.

    Doing that, I'll see the level maybe a finger width below the top mark. This is after backing out into the driveway, letting it idle for a minute or so, then back into the garage, shut off, and sitting for a few minutes. But I know from experience now to resist the urge to top up more: if I give it a few days, check again, it'll be right on the full mark.

    I'm thinking this might be the reason a lot of owners are seeing overfill from dealership oil changes: the mechanics are aiming to get the on the top mark, when the car leaves the shop, and just keep adding till they see that.