"Sucking oil past the rings"

Many years ago, my father told me it was a good idea to release the
accelerator once in a while whilst driving in order to "suck oil past
the rings". Apparently this action aided in lubricating the rings in
order to prolong their lifespan.

Two questions:
1) Is there any truth to this notion?
2) If so, is it applicable to modern cars?

"Hugo Schmeisser" > wrote in message
...
> Many years ago, my father told me it was a good idea to release the
> accelerator once in a while whilst driving in order to "suck oil past
> the rings". Apparently this action aided in lubricating the rings in
> order to prolong their lifespan.
>
> Two questions:
> 1) Is there any truth to this notion?
> 2) If so, is it applicable to modern cars?

I've still got a '56 Panhead Harley that I bought from a friend in '74. One
of the HD service manuals for those old bikes said to close the throttle at
cruising speed occasionally to lubricate the valve guides. Didn't mention
the rings, but the cyl. wall to piston clearance is about the same as the
valve stem to guide clearance. Should pull a little past the rings too, I'd
imagine.

Garrett Fulton

"Hugo Schmeisser" > writes:

>Many years ago, my father told me it was a good idea to release the
>accelerator once in a while whilst driving in order to "suck oil past
>the rings". Apparently this action aided in lubricating the rings in
>order to prolong their lifespan.

The pistons have the same up and down travel, and the same amount of oil per
revolution squirts out from the rod. The only things that I can think of that
change from the perspective of the motor when you let off the throttle a

- crankcase vacuum (and blow-by)
- rate of crankshaft rotation (and associated centripetal forces)
- if the spark timing varies, the ignition force on the connecting rods

I'm puzzled why "sucking oil past the rings" would be desirable. If it is
sucked past the rings, it will burn. A worn out engine allows oil to be sucked
past the rings, and this results in carboning, oil consumption, and blue smoke.
A properly functioning oil ring should leave just enough oil on the cylinder
wall to lubricate the rings as they travel down and then back up, but not more
or the rings will scrape the excess into the combustion chamber as they travel
up.

If anything I would think hitting the throttle hard would cause MORE oil to get
past the oil ring because of the blowby pushing it away from the cylinder wall.
Letting off the throttle in this case would burn less oil but I don't see how
it would aid in lubrication.

Maybe he is confused with 'lugging' the motor by opening the throttle past the
point where it produces a RPM increase. That used to be hard on bearings in
older motors but I don't know if it is much of an issue anymore.

Ryan Underwood wrote:
> "Hugo Schmeisser" > writes:
>
>
>>Many years ago, my father told me it was a good idea to release the
>>accelerator once in a while whilst driving in order to "suck oil past
>>the rings". Apparently this action aided in lubricating the rings in
>>order to prolong their lifespan.
>
>
> The pistons have the same up and down travel, and the same amount of oil per
> revolution squirts out from the rod. The only things that I can think of that
> change from the perspective of the motor when you let off the throttle a
>
> - crankcase vacuum (and blow-by)
> - rate of crankshaft rotation (and associated centripetal forces)
> - if the spark timing varies, the ignition force on the connecting rods
>
> I'm puzzled why "sucking oil past the rings" would be desirable. If it is
> sucked past the rings, it will burn. A worn out engine allows oil to be sucked
> past the rings, and this results in carboning, oil consumption, and blue smoke.
> A properly functioning oil ring should leave just enough oil on the cylinder
> wall to lubricate the rings as they travel down and then back up, but not more
> or the rings will scrape the excess into the combustion chamber as they travel
> up.
>
> If anything I would think hitting the throttle hard would cause MORE oil to get
> past the oil ring because of the blowby pushing it away from the cylinder wall.
> Letting off the throttle in this case would burn less oil but I don't see how
> it would aid in lubrication.
>
> Maybe he is confused with 'lugging' the motor by opening the throttle past the
> point where it produces a RPM increase. That used to be hard on bearings in
> older motors but I don't know if it is much of an issue anymore.
>


blowby will force oil back in the crankcase. High vacuum in the
cylinders on the intake stroke is what pulls the oil past the rings.
Not sure if that really works or not as it usually comes down the intake
valve guides first. But it's a good practice to vary the loading on the
rings anyway during break in.

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

"Hugo Schmeisser" > wrote in message
...
> Many years ago, my father told me it was a good idea to release the
> accelerator once in a while whilst driving in order to "suck oil past
> the rings". Apparently this action aided in lubricating the rings in
> order to prolong their lifespan.
>

Sounds like something you tell a 16 year old to trick him into slowing down.
How
old were you when he told you this?

Ted

Gotta agree with ted but to a different degree. Seems like todays
technology would prevent this from being effective. Years ago when
rings & pistons weren't what they are today, this probably would ring
true but I'm thinking in the world of today rings are made better & of
higher quality to seal things up nicer, not to mention the improvements
in oil rings (wipers). I'm also thinking that the air cooled bike
motor from that era would, indeed, have the piston clearance a little
looser than a water cooled motor in a car. Jus' theorizin.

Ted Mittelstaedt wrote:

>
> "Hugo Schmeisser" > wrote in message
> ...
> > Many years ago, my father told me it was a good idea to release the
> > accelerator once in a while whilst driving in order to "suck oil
> > past the rings". Apparently this action aided in lubricating the
> > rings in order to prolong their lifespan.
> >
>
> Sounds like something you tell a 16 year old to trick him into
> slowing down. How
> old were you when he told you this?
>
> Ted



Too young to drive! We were driving somewhere and I asked him why he
did this. Might have been mid-late '60s.

Nate Nagel wrote:
>
> blowby will force oil back in the crankcase. High vacuum in the
> cylinders on the intake stroke is what pulls the oil past the rings. Not
> sure if that really works or not as it usually comes down the intake
> valve guides first. But it's a good practice to vary the loading on the
> rings anyway during break in.
>
> nate
>

I suspect it does. I've seen cars with bad rings really smoke when you
backed off, as engine wound down. Smoke was worst on trailing throttle
than when accelerating.

Don Stauffer wrote:
> Nate Nagel wrote:
> >
> > blowby will force oil back in the crankcase. High vacuum in the
> > cylinders on the intake stroke is what pulls the oil past the rings. Not
> > sure if that really works or not as it usually comes down the intake
> > valve guides first. But it's a good practice to vary the loading on the
> > rings anyway during break in.
> >
> > nate
> >
>
> I suspect it does. I've seen cars with bad rings really smoke when you
> backed off, as engine wound down. Smoke was worst on trailing throttle
> than when accelerating.

Upon reflection you may be right. I remember having a new head put on
an old Valiant and it did smoke a little bit on overrun subsequently so
I know that in that case it wasn't valve guides. However I suspect
that valve guides are a problem, as I've ridden in cars that would lay
down a cloud after taking a hard corner but at no other time, which
makes me suspect oil pooling in the heads and subsequently being sucked
into the intake passages.

nate

"Hugo Schmeisser" > wrote in message
...
> Many years ago, my father told me it was a good idea to release the
> accelerator once in a while whilst driving in order to "suck oil past
> the rings". Apparently this action aided in lubricating the rings in
> order to prolong their lifespan.
>
> Two questions:
> 1) Is there any truth to this notion?
> 2) If so, is it applicable to modern cars?

My belief is that the answer is no to both 1 and 2. There is no throttle
plate to close for diesels and they seem to get by just fine (even
turbocharged diesels). While it is true that closing the throttle while the
engine is turning at high rpm will increase the vaccum in the intake tract
and cylinders, which may result in pulling more oil past the rings and
intake valve seals, I don't believe this is beneficial. I'd put this down as
an urban legend or old wives tale.

Ed