When is Overfilled Really Overfilled?

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Something I've wondered...

Even though the oil level at rest may be high from an overfill or just putting in all four quart bottles when the books says use 3.9 or 3.7 quarts, at startup the oil level will drop when the oil galleys in the engine refill. Wouldn't that negate much of the percieved problem?

Obviously, there comes a point of it doing damage...but when has anyone seen any real damage come from a little more oil than offically called for.
 
I never seen damage but my wifes Honda takes 1.2 quarts more to reach full than stated in the owners manual.

I have a motorycle that takes .5 quarts more than stated in the owners manual to fill.

I am sure millions of cars are over filled as we speak. The quick lube places do it all the time.

As long as the oil is not so high it is aerrating you should be OK I would imagine.
 
As long as it's not so high as to be above the windage tray. I'm sure it's generally quite a bit. Adding a whole extra quart, the oil level is probably only 1/2" higher and probably not making a difference.

Then again, a friend worked at a shop in high school and double filled a chevy truck, and both crankshaft seals blew out. So, it seems too much can be too much and cause some more serious problems than windage/aeration.
 
Define a "little more" than called for? I have to admit early in my oil change career that I put in an extra liter into my Neon. No problems for a couple weeks of normal driving and I forgot about it, but I got my scangauge in the mail and decided to see what rpms my car runs at.(Scangauge has a tach function, my neon doesn't have a tach)
So I was fooling around seeing what the shift points are at full throttle (6800rpm) and I see the oil light go off on the dash... All the high rpms had foamed the oil, I shut it down quite quickly and so far I haven't seen any effects from my error. That was 40000km ago and I run either full synthetic or 15W40 HDEO to help slow down any accelerated wear started from the lack of lube.
 
I've filled engines that call for 4.5 qts of oil with a filter, with 5 qts of oil for years. I would say depending on sump size being half a qt over in a small sump (say 4 qts) is not a problem. In say an 7-8 qt sump being overfilled by a qt shouldn't be a problem. My problem is being a qt over in anything might kick my OCD into high gear, and I might be inclined to drain some oil out.
 
Originally Posted By: bepperb
... Adding a whole extra quart, the oil level is probably only 1/2" higher and probably not making a difference.


If a theoretical sump (ie, with vertical walls) has a surface area of 1 square foot (for sake of argument) at the oil level, each additional quart will add 0.40 inches of extra reading on the dipstick.
 
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Something I noticed was that the dipstick tube will not push all the way down into the block, there is about a quarter inch of the tiny flange raised a bit, so my guess is the dip stick test is off. I tried smacking the flange with a chisel and hammer down more, but it's not working, i'ts killing the tiny flange. If the tube is raised a bit, would my ACTUAL oil level be LOWER or HIGHER than my reading. This confuses me.

Also, I've noticed the service manual says 3.9L refill capacity WITH oil filter. When I do a drain, and I pull off the filter too, how much oil is still trapped in the motor and where does it stay trapped?

Can I simply just do the 3.9L fill? In the past before my recent overhaul, each time I put in 3.9L like the service manual said, the dipstick read way higher than the max mark, I don't know why. Would this be because the dipstick tube may not go in all the way?
 
The design of a proper oilpan holding capacity is reflective on the proper dipstick marking. Engineers factored in things like certain tilting/operating angle of the vehicle, etc. to minimise any possibility of frothing the oil due to excessive oil level where the crank counterweight may "beat" the oil.

Frothing caused by too much oil (way more than what the manual stated) will cause air bubble introduction into the oil, and that may lead to air blockages on the crank/rod bearings especially under extreme operational conditions, which lead to bearing failures.

Oh and BTW: adding way more oil than factory spec'ed may also cause early oxidation due to delibrate introduction of oxygen as the crank "beats" the oil, sort of like an egg-beater but more aggressive.

Q.
 
I believe the factory's concern is overfilling could cause damage to the catalytic converter. It would be nice to know if there was a built in safety factor for going above the full mark on the dipstick. Such as 10%, etc.
 
My owner's manual specifically states that the oil level should be between min. and max. markings and to not overfill. So, as long as the oil level is between min. and max. your car is not under filled.

I know, I like to keep the oil at max level, but just because the oil is below the maximum, doesn't mean it's under filled.

Also, the oil capacity listed in owner's manual usually represents a dry fill, where no oil is in the system, so it is only logical that anything you drain will be less than that.

The oil capacity in my car is listed as 4.5 QTs with oil filter, but I always drain a little over 4 QTs, and that's how much it takes to fill the oil to the max level on the dipstick, if I put full 4.5 the oil level will be a little over max. so either way I would not worry about it.
 
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It is already taken into account that the sump level will drop a bit as oil fills passages and is splashed around.
This is why oil is checked at rest, after sitting a while.

In general, up to 1/2 qt. over should make no difference.
 
Years ago Dad had a bobcat engine overhauled (4 cyl gas). When it came back from the overhaul, the dipstick & oil was so clean no one could see it. The employees thought it was low and added a quart - several times.

Eventually everyone caught on, and as I recall it had about double the amount of oil it was supposed to. There was no permanent damage. A bit of paint on the dipstick and it was easier to see the oil.
 
Originally Posted By: KrisZ
My owner's manual specifically states that the oil level should be between min. and max. markings and to not overfill.


A friend who used to work for Honda says management always made them fill up only until the halfway mark between the low and high level marks on the dipstick. I suppose this way it was impossible to overfill the engine, not to mention also make a little more money. At any rate, said oil fill is definitely still within factory specs.

As a standard practice, at any oil change, I always bring up the oil level only till it clears the low mark. 75% into the oil change interval, I add fresh oil to reach the dipstick full mark to fortify the additive package that's now probably beginning to weaken. Of course, this might not work for somebody who hardly checks his oil level.
 
I've heard that running the motor too much below the MAX mark but higher than the LOW mark is not good for the oil pump, as the extra oil is there to cool it or something. Don't know how true that is for all engines, maybe certain designs.
 
The Windstar's dipstick shows something like this:

ADD |XXXXXXXX|
The manual states the engine is only over full of oil if the oil level goes past the F in FULL. It takes the manuals' stated capaicty to reach the top of the hash marks. I'm guessing it would take almost quart to reach over-filled?
 
`When I worked at a dealership we were encouraged to fill it a hair or more above the full mark so that the customer felt like he got his money's worth and not ripped off. I didn't as a rule, but the one-in-a-million customer who actually checked their oil on the spot did and he ripped me a new one for overfilling it (had to drain it and it was a black mark against my job performance).
 
It seems to me that the only way to know if an engine is truly overfilled is to find a way to measure the clearance between the bottom of the pan and the bottom of the crank. You would hope that the dipstick is calibrated for this, but I doubt they are very accurate.

I'm pretty sure the |xxxxxx| band on the dipstick is there just to give the customer some wiggle-room when topping off. If it was just a single line, people would go crazy adding a few ounces here and there to make sure it was close. With a range, the customer knows that he just has to add a quart when it says "add".

The downside of aeration is that the more bubbles in the oil, the bigger the volume of the oil. So it just whipps up even more.

This just made me wonder whether sump capacity and sludge/varnish/OCI are related. Just as an anecdote, it seems like the cars I've had with higher sump capacities seem to have cleaner engines. My Ford with the 2.5 Duratech took darn near 6 qts and was clean as a whistle after 8 years and 130,000 miles. My Grand Prix with a 4.5 qt sump capacity is filthy. The oil always smells awful.

It would seem to have a direct effect on OCI- an engine in operation has a certain amount of oil "working" in the engine- for each engine rev, there is say an ounce of oil getting smashed by bearings. It doesn't really matter what the actual amount is- every individual engine will "work" the oil so hard with each revoloution. So in identical engines, one with a 5 qt sump and one with a 6 qt sump, the oil in the engine with the smaller sump is getting worked 20% harder. Or putting it another way, after a million engine revvs, that oil is 20% more worn out. And since it theoretically runs that much hotter, you might be reducing its life by another 10-20%.

Something to consider... I wonder if the OCI computers take this into account?
 
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