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Discussion Starter #1
I've read threads on overfill and such. I assume the two dots on the dipstick are the low and full mark? Where does it say how much oil to put in the owner's manual? All I found was that it's 1.5L between Low and Full. Cause I just checked mine and it's way over the full mark and was wondering how they can overfill the oil?
 

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I believe it's 3.8 or 3.9 quarts.

So I tell them to only put 3 and a half bottles of Mobile 1 in, and leave me the leftover half quart in the car.

It's never overfilled this way, and every 7th oil change, I'll get it done for just the cost of labor and a filter. :)
 

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Page 312:

ENGINE LUBRICATION
Oil capacity (drain and refill), L (qt., lmp.
qt.):
With filter 3.7 (3.9, 3.3)
Without filter 3.4 (3.6, 3.0)
“Toyota Genuine Motor Oil” is used in your
Toyota vehicle. Use Toyota approved “Toyota
Genuine Motor Oil” or equivalent to satisfy the
following grade and viscosity.
Oil grade:
API grade SL “Energy–Conserving” or
ILSAC multigrade engine oil.

However, experience by all says 3.5 quarts max.
 

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Probably 100,000 Prius are running around sucessfully with four qts. of oil in them indicating about a 1/16 in. high on the dipstick. This seems the way they come from the factory and is what a Toyota dealer will service them with when the filter is also changed unless you make a "big stink".
The next question to be asked is will this practise do any harm? I guess you have to accede to the knowledge of the guy that is warranting the car. Which is the safer side? Oil in an internal combustion engine does more than lubricate the engine. It helps with the cooling. More passing through it is better than less. I believe my dealer is correct and he would charge me just as much for 3.9 qt.s as he now does for four.
One tenth of a qt is less than two "shot glasses." For cooling purposes, two shot glasses high does much more good than running almost a half of qt. low.
No car manufacturer would build a car without a huge safety factor built in.
 

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Hyperion is correct in all aspects. I've read tens of posts (not quite hundres, but give it a few months) and there is this continuing debate about that .10 of a quart.

And just to bolster his comments, I've read hyper-cautious responses about overfill from a number of Prius posters saying that any level of overfill is bad, and that just isn't true. I like to put it this way. If a dealer or oil change shop put in 5 quarts of oil, that would be genuine overfill. 4.5 quarts of oil would also be a pretty serious overfill. However, it takes 10 .10s of a quart to make a full quart. So, an "overfill" of .10 is nothing. If there is not enough clearance accross the entire volume of the oil sump (heigth, width and depth) to take on an extra .10 quart of oil, then Toyota has not taken real world usage patterns into account when engineering this product. I'm pretty convinced they have taken into account these factors as I am running a full 4 quarts of Mobil1 in my Prius and height above the top dot on the dipstick is nothing.

Let's also consider this. Some manufactuers are moving toward dry sump oil systems, where the oil system sucks all the oil out of the sump and keeps it in continual ciruclation at all times. In those applications you would absolutly not ever underfill your engine. So, if that is the coming trend in engine design, why would we do it today on conventional sump engines.

It just doesn't make a whole lot of sense to me to worry about .10 of a quart.
 

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Remember... It's 3.8 quarts in the front tires and 3.6 in the rear. Less will reduce your mpg.
 

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hyperion said:
And that would be an excellent way to end this thread!
How about we knock off the running out of gas thread at the same time. I don't expect anyone to really admit to doing something this stupid on the internet!
:lol:

Only if we stop complaining about the lack of instrumentation as well!

Never mind ... we would miss that too much!
 

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Did you all forget to read this point: experience by all says 3.5 quarts max.

Even 3.9 qts will put you over the mark.
 

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Discussion Starter #13
Got the mechanic to inspect it. It's quite overfilled so they'll drain the oil, check my glovebox release button (early wear and tear) and fix my rear bumper (has a little bump on the right side like at tumour lol)
 

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Put in three quarts. This leaves the level halfway between ADD and FULL (thus no possibility of an overfill), you'll spend less on oil, and there'll be no half-empty bottles of oil to fool with.

The advice to use too much oil to help "cool the engine" is, uhh, curious. Additional cooling via the oil system just means that the engine will run longer to keep itself at it's operating temperature. Using more oil and more gas than necessary is not why I bought a Prius.

But hell: it probably doesn't make a rat's ass of difference either way.
 

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It sure could make a lot of differance if your car starts consuming oil and you aren't checking every day. What in the heck is the matter with erring on the safe side rather than the other. Put in four qts, as the dealer does with a filter change, throw away the cans, and drive off on the safer side. Three qts probably is fine as you say as long as you are content to check the quantity daily. Last I checked, even a qt. of Mobil "1" wasn't that expensive. The whole object is to recognize where on that dipstick the engine is running normally and if "any" changes are observed to look into the matter. We've all heard the term "my car burns one quart of oil every two thousand miles." You then determine a reason. It's a lot easier spotting any changes from the appearance of a full dipstick rather than one indicating about the 3/4 spot on a diptick with only 3 and 1/2 qts in the engine. And really, you've never heard of oil cooling? Then you've never owned an older air-cooled VW or any engine with a dry sump. Have you never heard of the term oil or transmission cooler? Those fluids get darned hot and heat is bad. It's so hot in that engine it only takes a short time to bring the oil to operating temps.
 

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Speaking of VWs, it has been claimed (by John Muir, no less) that additional oil doesn't run cooler, it just takes longer to warm it up. But once to operating temp, more oil doesn't mean a cooler running engine. Not sure if I agree or not, but my solution was the later "doghouse" fan shroud, bigger fan, aluminum Type III oil cooler, and THAT made a helluva difference.
 

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John Muir was into trees and before the dry sump and oilcooler engines every hotrodder in California built over sized pans with cooling fins on the outside surfaces to go along with the dual and triple carbuerators, and shaved or Edlebrock heads. My first Jag a 1952 XK 120 coupe had I believe a fourteen quart pan on it. My 58 Lotus Europa with a blown Renault four cylinder engine took eight. My Cadillac takes 6 1/2 quarts and my Plymoth Voyagers six quarts. 3.9 qts is very little oil, unless you give the quantity lots of attention. There becomes little margin for error and starting with three qts removes that margin.
 
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