Overfilling Oil

General feeling seems to be a decrease in mpg, at the very least.

 

The notion that the cranshaft and connecting rods might be splashing in high oil has been discounted. In some peoples' minds at least.

When oil is installed to the Prius engine too rapidly, some of it certainly seems to find its way into the intake manifold. I believe this can occur whether or not the final fill is "over". When Prius has oil there it expresses displeasure in a few different ways, probably including reduced fuel efficiency.

 

<div class='quotetop'>QUOTE(newtoprius @ May 24 2006, 10:45 PM) [snapback]260733[/snapback]</div>

Well, the same as with any engine.. if overfilled to the point the crankshaft is in the oil, it will foam the oil to the point that air can get sucked into the pressurized oil system..

Bearings don't like air circulating through them...

Also the "windage" loss in the crankcase would go up dramatically. i.e. the source of the loss of mpg.. While the website below is a discussion of helical gear loss, conceptually many of the same things occurs in the crankcase and the definitions of the terms is still correct.
http://www.geartechnology.com/issues/0905/mba.htm

btw I've read here http://www.ornl.gov/~webworks/cppr/y2001/rpt/121813.pdf the oil misting (for cooling reasons) in the MGs is a one of the larger sources of energy loss. Also some good pics of the internals in this document..

 

My Prius teck told me when I first got my Prius that it screws up the various sensors and something else in the intake and causes a no start condition.

 

<div class='quotetop'>QUOTE(newtoprius @ May 27 2006, 07:51 AM) [snapback]261761[/snapback]</div>

ok tell us what the H happened to lose the PSD unit

 

<div class='quotetop'>QUOTE(dandeman @ May 27 2006, 09:13 AM) [snapback]261736[/snapback]</div>

this depends on exactly how much oil you're talking about. if someone managed to shove 6 qts of oil in there, and the computer did not stop the engine (which would normally throw the P3191 no start code) sure, you could have damage. the prius is a slightly different case than the average car. the computer will not start the engine if it doesn't like the oil level.

in the case of a slight overfill, it blows most of the excess out of the PCV valve and you can see it in the throttle body.

the oil you're talking about in the last paragraph is WS ATF, not motor oil. there are no consequences of a motor oil overfill on transmission function.

 

I think adding the fresh oil too quickly has caused more grief than adding a bit too much. If you carefully follow the PCV plumbing it should be apparent if you flood the cylinder head with oil, the excess will flow into the intake.

I would still like to check my intake, but does anybody know a safe way to move the electric throttle positioner? I don't want to jam a screwdriver in there, what if it's a stepper motor with plastic gears? Would be pricey to fix.

This is a concern to me as I used to regularly clean the IAS/TB assembly of my 2000 GMC Sierra. That involved removing the IAS stepper motor and pintle valve. The shop manual clearly warned you not to try to move the pintle valve by hand or you would break the plastic gears inside the stepper motor. Afterwards you still had to do the Idle Learn Procedure.

 

Hello,

I think this happened to me. I wrote about this in another post. Now, I can't get to start the car. How could I go forward?

 

A tag-along question here regarding overfill: The owners manual for my 2007 states 3.7 quarts with filter change. Nice round number. Will just adding the entire final quart to the crankcase cause any issues? Other than potential blow-by at the fill cap and the PCV, if I could easily see it? Are there potential seal issues or anything like that? I too am a noob and while the oil was very clean when I purchased the car, the oil level on the dipstick was above the full mark. I changed it despite the indicated age and condition of the oil with Mobil1 5w30 and slowly added the 4th quart until there was approximately 1/4 left in the quart container. The filter was changed as well. No over-full issue now on the dipstick but I am curious if the additional 1/4 quart over time could impact anything.

 

It’s not a good idea to overfill the engine oil.

As you said overfilling will cause more blow-by that will cause more oil to go through pcv-valve and piston rings. That will cause more wear on pcv-valve and also it will cause engine to burn more oil. If pcv-valve fails it will cause even more oil burning. But even with working pcv-valve more oil burned in the engine will cause more deposits on combustion chambers, piston rings, and oil return holes. Deposits in combustion chambers can cause knocking. Deposits in piston rings and oil return holes can cause engine to burn more oil.

And because oil burning can cause deposits and deposits can cause oil burning this can cause a cycle that turns your engine into oil burner.

 

Would anyone of this cause the car to not start up?

 

Geesh, that's a new one for me. I do dump it in as fast as it'll go, without overflowing the funnel. Could that seriously be? That's not good.

I would put in the spec'd amount, chances are in a few months level may drop due to consumption, and you can use the left over for top up.

FWIW, I buy oil in a bulk container, rounding up/down becomes meaningless.

 

Quick update that my car was able to start back up and is now up and running. I just had to make sure the High Voltage battery was properl connected back up.