Advantages to overfilling oil?

[Jimmy9190]

I know most of us here believe it is OK if you over fill the oil by up to half a quart. I believe the same thing myself. I am just wondering though, is there any real mechanical advantage or benefit for the engine's innards if you do overfill the oil sump on purpose? Would it help out an older, higher mileage engine or will it cause any problem with power or MPG?

I usually have to add 1/3 to maybe 1/2 quart about 2300 miles into my OCI. I just wonder if I overfilled on purpose would it be a help or a hinderance to my truck?

Thanks.

 

[gfh77665]

No effect either way.

 

[flwxman]

I would think, depending on the application, you may be able to slightly extend your OCI due to the higher quantity of oil. You may start to get some, or more, oil splash from the crankshaft, which could affect the oil's and engine's performance. Otherwise, not really sure. Having said that, I usually fill to (or slightly below) specification, and just top off when necessary. My Spectra calls for 4.2qt, and I usually just put in 4. My Accord calls for 4.5qt, and I put in 4.5qt to my best guess.

 

[The Critic]

Yes, on the priuschat forums the guys there would rather keep the level 1/2 qt low than have it overfilled. Supposedly they have been able to notice a reduction in fuel efficiency in the event of an overfill.

 

[ARCOgraphite]

Most all Owners Manuals say you will 'VOID the engine warranty' if the engine oil is overfilled and to 'remove excess oil if noted after an OC'. So, yeah, this is BITOG - just IGNORE that

The real question is to define what is "overfilled" for each application - could be 1 cup in some and 1 litre for others. ...

I try to stay within 1 cup on either side of the line. You can really swamp the PCV and intake with oil if you overfill and foam the oil which can lead to bearing failure. On the plus side at times I may have notice improved very low engine speed running with excess oil(again 1 cup or so) in the sump on many cars - this could easily be a placebo. Varying oil volume also affect the PCV system by varying the acoustic resonant frequency in the crankcase. This is another area of engine science and design altogether ignored by most car guys and mechs.

 

[UncleS2]

I try to avoid over filling by anything over 1/4 qt, in any vehicle I've ever owned. Example- yesterday I changed the oil on the 3.9 Dakota, 4 qt capacity total. I verified that a longer filter was a *bad* idea, used standard filter, & after letting it drain for ovr 1/2 hr, filled with 4 qts of Havoline, plus about 4.5 oz of LC. Some of the LC will "cook out" in the next 1000 miles or so. It just didn't seem worth keeping back 4 oz of motor oil. Not much of an overfill there!

Here's a thought- you may find your overfilled truck uses more oil, & shows the same oil level at the same mileage. I'm not saying don't try it, and if it does still wind up x amount low at 2300 miles you haven't hurt anything. I've had at least two long term vehicles that tended to find their own oil level. Once I quit chasing the full mark, they'd level off at about 1/2 qt low on one, about 1/4 to 1/3 qt low on the other, & then hold that level for many more miles.

I'd say you have nothing to lose at plus 1/3 qt, give it a try!

 

[tinmanSC]

Err... A cup? I find it utterly impossible to believe that 1 cup of oil could do anything noteworthy in a crankcase. A quart, ok, but a cup???

 

[The_Jeff]

They say on the contour/mystique 2.5 v6 you should have a little extra in to avoid starvation on cornering.

 

[Jimmy9190]

Thanks for the replies. I believe I will just continue on filling w/4 quarts and adding a little oil if needed later on during my OCI.

Thanks again.

 

[KrisZ]

My Mazda manual says not to overfill, I try not to and usually prefer if the oil level is a bit under the full mark.

I think it's a psychological thing for people to say overfilling is good, more is better right?

I see so many people saying their sump is 4.5 qts. and they just dump the whole 5 qts. in because they don't want to deal with 1/2 qt bottles, but I rarely see people with similar sumps saying they put in 4 qts. for the same reason. They can go either way and still use whole bottles, but most choose to put in more

 

[tinmanSC]

Originally Posted By: Stuart Hughes
I verified that a longer filter was a *bad* idea,

Why was it a bad idea? Do you have a link to your posts about this? (i'm assuming you posted about this.)

 

[chet2]

i overfill my bro in laws car by 1/2 qt cuz if i dont he is type of person to never check and rarely change oil, sis is same way

 

[Dave Hess]

All my cars for the past 25 years I add 1/2 quart extra.

 

[K20FA5]

I overfill mine too. I usually just round up and since I buy 5 qt jugs at Walmart, my wife's Pilot calls fro 4.5 qts, I put in all 5. My Frontier calls for 5.5 qts, I put in all 6.

I don't get any foaming or even air bubbles on the dip stick and nither car has burned any oil.

 

[gfh77665]

Again, < 1qt.= no effect.

 

[4ever4d]

Arco,could you please elaborate further on this statement?:Varying oil volume also affect the pvc system by varying the "ACOUSTIC RESONANT FREQUENCY" in the crankcase i am not certain what this is but you have certainly peaked my interest!I am to assume you are talking of the sound frequency generated inside an engine does this play an important role in engine function and performance?

 

[SLCraig]

I never overfill, always to full line only.
Only advantages to overfilling is that if it doesn't actually burn off faster, you can go longer between topoffs if the car is an oil burner.
I'm ok with opening the hood once in a while so I don't overfill.

 

[CATERHAM]

Originally Posted By: eljefino
They say on the contour/mystique 2.5 v6 you should have a little extra in to avoid starvation on cornering.


That and the oil starvation that can also occur during hard braking is the only beneficial reason to over fill the crankcase and is best done with the aid of an oil pressure gauge.
A couple of my cars have this problem if the oil level isn't very close to the full mark so I may overfill by 200 mls but no more.

 

[fdcg27]

I think Arco has some pretty extensive knowledge.
OTOH, Arco has also ruined a number of engines based upon his own posts.
He may or may not be a very good source of information and advice.
For my part, the 4.5 quart '99 Accord and '97 Aerostar always got five quarts, and I never saw any ill effects in either.
The ~4.5 quart Subie also gets five, as does the 4.5 liter BMW.
Both seem content with this.
The only real advantage is that I prefer to avoid having a bunch of orphan half quarts laying around.
The '97 Accord takes, and gets, four quarts, and after 4K on its current fill of PP, hasn't used a measurable amount.
It is very posible that the extra .5 quart in the others is consumed more quickly than the remaining fraction.

 

[UncleS2]

Originally Posted By: tinmanSC
Originally Posted By: Stuart Hughes
I verified that a longer filter was a *bad* idea,

Why was it a bad idea? Do you have a link to your posts about this? (i'm assuming you posted about this.)


No posts except the one above, I did that oil change only yesterday. 2nd oil change since I bought the truck and had the local svc station do the first one(with my oil & filter) so I could walk around under it on the lift & look for any bad surprises.

A longer than specified oil filter looks like a bad idea to me because there's very little clearance at the filter's dome end. It mounts hanging down at ~45* angle, mounting plate at right rear of block just above oil pan. Dodge Dakotas mount the 3.9 & 5.2 engines(maybe others) off center a few inches to the right(USA Passenger side), which reduces clearance between the filter mounting plate and the frame.