Too much oil?

I think the main problem with overfilling the oil is that it makes a no start condition(oil gets backed up into the intake manifold. I don't think it causes any long term harm to the engine.

 

What I cannot figure out is that, if going 1/8 inch over the full mark can be bad for the engine in any way, why didn't they put the full mark lower down on the dipstick? It should be understood that some people, occasionally, (including service mechanics) will slightly over-fill, especially with a peculiar capacity. Put the full mark lower on the dipstick, and problem solved.

Either the danger of over-filling is an urban legend, and really not an issue, or Toyota is cutting tolerances much too close for a frequent maintenance item.

 

Only ferrus metal. Won't trap aluminum, copper or brass, which oil analysis has detected during break in.

 

I have come to believe the overfill thing is urban legend. Not saying you should overfill, but there is just no way that I know of that this could happen.
I'll be changing my own, so I'm not too worried.

 

We have better oils now, so some of the reasons of why an overfill is bad are no longer as important.

However, overfilling the crankcase can allow the crankshaft to whip oil in the bottom of the pan into a froth. This can cause air pockets to be pulled into the oil pump, and cause lubrication starvation.

This could also cause the oil to start to break down prematurely, again degrading the lubrication capacity of the oil.

Overfilling the sump can cause too high oil pressure, and cause seals to be damaged, making the car leak oil, or damage the oil filter.

Finally, too much oil will cause a drop in fuel economy, again due to added resistance as the crankshaft has to turn through a pool of oil.

Our engines utilize a "wet sump" system, where excess oil is stored directly below the crankshaft.

 

yes but....
Only exception I'd take to what you said is that...if overfilled and the crank does pummel the oil, it would foam the top, not the bottom where the pickup is.

However - The "problem" is stated as oil in the Intake. Other than through the PVC valve...where? And you'd clog the PVC valve before that happened.

Not endorsing filling oil pan willy nilly, just saying that I think this is urban legend. I am, however, very open to being proven wrong.

 

The only example that I can think of, is to whip scrambled eggs with a blender or wisk. Notice how air pockets are suspened throughout the eggs? It's the same concept with the oil.

 

Funny you guys are discussing this. My Prius comes later today, but my parking spot is currently occupied by my Saturn, which refuses to start. I happened to overfill it with oil the day before it stopped. Could this be why it refuses to start? All else seems okay (lights come on when door opens, I can hear the starter motor clicking when I turn the key, and even a jump-start didn't do it)

Either way, any suggestions on how to drain the excess oil? I'd prefer not to jack up the car (I rent, so I don't think my landlord would appreciate my possibly messing up his driveway with jack-marks and oil spill), but I can't think of another way.

 

Ok, I'll buy it. But, I think you'd have to overfill a good bit for that to happen.

Still think the intake thing is urban myth.

 

All I can compare to is the problem I had with my 2000 GMC Sierra when it was new. It guzzled oil, a liter every 800km was doing good.

It turns out the PCV system was WAY too aggressive, and it would literally suck the oil right off the rocker arms. Incidently, this may have contributed to some rocker problems with Vortec 5.3 motors.

GM finally had a "fix" of sorts: a redesigned PCV valve with a restrictor in it. The d*** thing also made a really annoying whistling sound. I think my motor developed asthma, it sure had that wheezy sound. Grr.

Depending on how much clearance is at the rod lowest point of travel, and the oil fill level, you can easily whip up motor oil. A windage tray may or may not cure it. It doesn't take much in the way of contact, just the air pressure from a crank rod whipping around can stir the oil up.

So don't say it's Urban Legend. If my GMC truck could suck oil right off the rocker arms with NORMAL oil fill levels, imagine what an overly sensitive PCV system might do if overfilled. There has to be a reason why Toyota is so concerned about oil overfill in the Prius.

 

I'm not saying that overfilling is not bad. I'm questioning the idea that the full mark on the dipstick is the actual exact point, beyond which damage can occur.

And I'm not asserting that it is not. I'm just asking, Would Toyota actually leave no room for error at all? Not even an eighth of an inch for error, knowing how prone people are to small errors?

 

Had an old Atomic 4 in a boat once that had stupidly been bedded in so a person couldn't get at the plug in the pan. Had to remove old oil using a power-drill pump which had a thin intake tube that was placed in the dip stick tube. Maybe these pumps are still around for folks to use when some idiot overfills their Prius sump. :mrgreen:

 

The multiple reply's

Jayman - No one is losing oil, from what I've read. While your GMC issue is hard to imagine, its obviously true. But I assume you were losing oil. That would be the difference.

And, as Daniel mentioned, I just have a problem with there being that low of a tolerance in a production, non-performance car. I mean, windage trays, crank scrapers, baffled pans, all good things, but are meant for race cars.

And Canuck, Mityvac makes such a thing, but it build pressure with a bike pump. Is good.

 

Yeah, some of the people here seem to go hog wild over an eighth to quarter inch over. I had that much over when delivered, too. I didn't worry about it; figured Toyota had some tolerance built in.

But, overfilling, in general, can be bad. You can have the oil whip into froth (like whipped cream), see Click&Clack, you can have it sucked into the intake, but a eighth inch come on, get real.

Others will say it'll hurt your milage; possibly, but no one has shown *any* evidence that an eighth inch over the fill mark will do so.

Thanks,
Shawn

 

the PCV circuit is an open loop where by it takes fresh air from the air cleaner and pulles it into the engine and then the PCV valve pulls the air, now laden with hydro carbons, water vapour and various other vapours, into the intake manifold, below the throttle plate, and then into the engine and burns it as if it were more fuel. If the engine is grossly over filled to the point of crank whip then the excess vapours can enter the air cleaner. If the engine is completely filled to the point of the PCV valve being submerged in oil then it'll enter the engine and possible cause mechanical damage. Engine's with worn rings and cylinder walls can put enough blowby into the air cleaner to saturate the air filter but to cause the no start complaints, I doubt that is a reality. I have seen engines with enough oil in them to submerge the PCV and on older engines with road draft tubes I've seen oil running out of them. These are on forklifts where the hydraulic pump is driven off the camshaft drive gear, and the seal on the input shaft is leaking and pumping hydraulic oil into the crank case. 1/8" over full I doubt will ever cause any noticable effects.

 

My last nissan had too much blow-by, causing oil deposits to get on the MAP, and the air cleaner. Probably caused by a partially plugged catalytic, and eventually damaged rings.

coondognd, does it turn over, or not even moving?
In order for an engine to run, you need spark, fuel, and compression.
If it's turning,
Be sure you have spark: take a sparkplug out, connect it back to its wire, lay the screw part of the plug on a good ground, but away from the now open sparkplug hole, and give it a few cranks. If you see spark, good.

Fuel: more difficult with fuel injection. I suppose you can see if you smell gas when you crank the engine with the sparkplug out if its hole.

Compression: use a compression testor.

If the engine won't crank, either your starter is bad, or the engine is seized. It could be fluid locked. Try taking all the plugs out and try to crank. If there's fluid in there, it will be thrown out.

 

Note that the lower mark is ADD, not EMPTY. If we posit that Japanese practice puts the nominal operating level halfway between the ADD and FULL marks, then yes, the FULL mark could well indicate the do-not-exceed level. It would have a useful explicitness to it, requiring no guesswork about how much margin there is: the margin would be precisely the range between the ADD and FULL marks. By some strange coincidence using exactly three US quarts of oil puts the level almost exactly halfway between the ADD and FULL marks. How 'bout that! :_> (One could argue that there must be *some* margin for error beyond the FULL mark, since many Prii reported here came from the factory overfilled by an 1/8 inch or so. But is that really the factory level? Do we know that Toyota USA does not change the oil when the car arrives onshore, and that this is their mistake? Do Japanese, European or Australian owners find the same initial overfill?)

 

I spoke with my local Toyota Prius tech and he DID mention that 3 litres would be acceptable for a fill, including replacing the oil filter. He claimed he would prefer just putting in 3 litres, but the customer would notice the oil level between add and full and raise holy h***.

They have had some cars and trucks come in with problems after a customer changed the oil themselves. It was usually some odd capacity, like 4.5 or 5.5 litres, so the customer dumped in the remainder. Usually, all that happens is the excess oil vapor causes problems for the PCV valve.

Apparently, they're only anal-compulsive about overfill on the Prius, not the rest of the fleet. So there must be a good reason for Toyota to be so concerned about too much oil in the Prius

If you only put in 3 litres, I would think if you get into the habit of checking the oil once a week, you would not have to worry. I've never owned a Toyota that consumed more than 1 quart every 8,000 miles.

The dipstick issue is something to consider though. Does F mean "Full" or does F mean "OVER full?" On my old 1984 Ford F-150 with 302 V8, the dipstick has the following marks: Add, Full, and "O."

The "O" is about 3/4 inch above the Full mark, and is used to indicate Overfill. I've never filled enough oil to bring it up to the F mark, usually around halfway.

Remember: too tight can be just as bad, if not worse, than too loose. Too full can be just as bad, if not worse, than too low.