Overfilling with oil: any concern?

[Charles Packer]

On my wife's 2001 Forester, I had to have the head
gasket replaced on one side. The mechanic, whom we
consider to be competent, based on our previous
experience, overfilled it when he replaced the oil.
Should I be concerned?

 

[Asbjørn]

On my wife's 2001 Forester, I had to have the head
gasket replaced on one side. The mechanic, whom we
consider to be competent, based on our previous
experience, overfilled it when he replaced the oil.
Should I be concerned?

Yes, depending on How much?

 

[1 Lucky Texan]

On my wife's 2001 Forester, I had to have the head
gasket replaced on one side. The mechanic, whom we
consider to be competent, based on our previous
experience, overfilled it when he replaced the oil.
Should I be concerned?

I dunno if anyone can say precisely at what point it could be a
problem. I personally would probably allow 1/2 or slightly more quart
overfill. The issues, supposedly , are; the crankshaft could beat the
oil to a foam, compromising the pumps ability to move the oil. Might
be problems with excess oil being pushed out thru the crankcase
ventilation system too I guess.

 

[John]

I dunno if anyone can say precisely at what point it could be a
problem. I personally would probably allow 1/2 or slightly more quart
overfill. The issues, supposedly , are; the crankshaft could beat the
oil to a foam, compromising the pumps ability to move the oil. Might
be problems with excess oil being pushed out thru the crankcase
ventilation system too I guess.

Doesn't it also raise the oil pressure?

 

[1 Lucky Texan]

Doesn't it also raise the oil pressure?

I doubt it would affect the oil pressure relief valve. i suppose it's
'possible' - but I don't know what the mechanism would be to cause
that.

 

[Asbjørn]

Doesn't it also raise the oil pressure?

Why in the world would it do that?

 

[Charles Packer]

Why in the world would it do that?

Actually, that's the story I heard somewhere -- that
overfill of oil would "blow your seals"...but if there's
a pressure relief valve, then the engineers have thought
of that too, haven't they? In this case the oil has been
so overfilled that no amount of wiping off the dipstick
and reinserting it shows where it was filled to.
The radiator reservoir was overfilled also. Sigh...
this is why I'm happy to do the regular oil changes of
our cars myself.

 

[1 Lucky Texan]

Actually, that's the story I heard somewhere -- that
overfill of oil would "blow your seals"...but if there's
a pressure relief valve, then the engineers have thought
of that too, haven't they? In this case the oil has been
so overfilled that no amount of wiping off the dipstick
and reinserting it shows where it was filled to.
The radiator reservoir was overfilled also. Sigh...
this is why I'm happy to do the regular oil changes of
our cars myself.

I had bad luck with the cheapo siphon I tried years ago - but there
ARE devices that will let you pump the oil out of the dipstick tube,
some of them attach to a drill motor I think. Might be a little easier
if you could borrow/rent one. Otherwise, you're gonna have to pull the
drain plug.
It can be tricky sometimes to get a reading on my soob's dipsticks.
Just triple check before getting crazy!

 

[Bill Freeman]

Overfilling will not raise the oil pressure from the oil pump. That
pressure is limited by the oil pressure relief valve. It would
probably lower the oil pressure if the oil turns to froth from direct
contact between the crankshaft and the oil level in the pan.

Overfilling might blow oil seals or pan gaskets and valve cover gaskets
due to increasing the pressure in the crankcase from whipping the oil
into a froth from contact with the crankshaft. The reduced air space
in the crankcase due to overfilling would contribute to the crankcase
pressure increase.

If it seems OK after draining the oil to the proper level and running
for an hour or so, it's probably not caused any damage.

 

[Charles Packer]

Overfilling might blow oil seals or pan gaskets and valve cover gaskets
due to increasing the pressure in the crankcase from whipping the oil
into a froth from contact with the crankshaft. The reduced air space
in the crankcase due to overfilling would contribute to the crankcase
pressure increase.

If it seems OK after draining the oil to the proper level and running
for an hour or so, it's probably not caused any damage.

On that note, I called the shop and told the manager that somebody
there had overfilled the oil. He agreed it could be "bad" and told
me to bring the car by to have it corrected. Stay tuned.

 

[Charles Packer]

The folks at the shop told my wife it was about a half-quart
overfilled. Whatever. It had looked like a lot more to me.
At any rate, they corrected it.

 

[1 Lucky Texan]

The folks at the shop told my wife it was about a half-quart
overfilled. Whatever. It had looked like a lot more to me.
At any rate, they corrected it.

I THINK most oil change shops have a central pump and the fill nozzle
has a dial selector. It may not be able to adjust accurately or in
half-quarts so maybe they err on the side of a slight overfill?

anyway - glad it got corrected.

Carl