Curious...

Run the numbers for average temperatures from April to November in
Southern Ontario where Tegger says on his web site that his car
resides. We are talking about a change in average temperature of
around 27 degrees F. The difference in oil volume with a change in
temperature of about 30 F is about 0.045 quart. This is comparable to
the reading error. Plus, like reading error, with enough readings, it
is going to average out.

 

jim beam wrote:
oil expands when it

Except that in the real world it makes no significant difference in
terms of accuracy. It takes hours for oil that is in the bearings, oil
passages to the bearings and head and other crankcase locations to drain
back to the pan. That means that in many engines you get the exact same
reading when you check the oil a couple of minutes after hot engine shut
down as you do when it sat over night.

Anybody with a brain and sufficient curiosity will easily determine on
their own how this works. If you check the oil every 30 seconds after a
hot shut for a period of hour (about 120 dipstick checks) you will be
convinced that the reading is constantly changing.

-jim

 

you should sign up to defend gasoline vendors against this kind of
frivolous lawsuit:

<http://rawstory.com/rs/2010/0605/gasoline-costs-hot-weather-class-action-lawsuit-alleges/>

 

Yes and that in and of itself should make anyone suspicious of the
methods used to acquire the data.


There is an obvious bias in the way the measurements were made. The
miles/qt is almost always around 400 miles less for the measurements
labeled 1st than for the measurements labeled 2nd. There is not enough
info to determine exactly what the source of that bias is. All that can
be said is it is extremely unlikely that an honest and accurate
accounting of how much oil this engine consumes would show that the oil
is being consumed at a slower rate the longer it stays in the crankcase.

-jim

 

I'm glad to see that I am not alone in hating those Web forums.

 

The CTE of unused motor oil is 0.00039/°f
http://www.engineeringtoolbox.com/cubical-expansion-coefficients-d_1262.html
(this is actually a pretty handy piece of software)

So a 30 degree F delta equates to a +1.17% change in volume at +30°
http://www.engineeringtoolbox.com/volumetric-temperature-expansion-d_315.html

At a mean of about 1600 mi/qt, that would equate to a max error of
18.72 miles. Considering the measurement method, that is probably not
too bad.

 

If they had proper threading and default quoting, they'd at least be
bearable in spite of all the glitzy, busy graphics.

 

so set up your own. use slashcode. it's free and it's full threaded.

 

Interesting. Ambient temperature was one variable I couldn't control, so
it's nice to know it doesn't have much effect on the oil level.

The graph says there appears to be no connection between ambient
temperature and oil consumption.

 

It may be interesting to graph each 1k miles separately to see the
trends when you have enough data. Since we now know that there is a
difference of 0.039% volume change per degree F, you could use that in
your spreadsheet calculation if you so desired.

Here is a fairly simple explanation about oil and evaporation
http://www.newton.dep.anl.gov/askasci/chem03/chem03025.htm

I do know that hygroscopic polymers (petroleum based products) absorb
moisture, and to remove it prior to processing it needs to be driven
at a specific temperature (temperature dependent on type of polymer
and time), in a -40°c or lower dew point system that has the ability
to either absorb the moisture through desiccant, or exhaust it
(compressed air drying systems). If there is no way for the moisture
to be absorbed or escape, it will not "dry" or removed.

 

I do have all the the ambients when checked at start/end, so I could
make a graph revision incorporating that.

Nice.

ASTM D-5800 is desgned to specifically address evaporation, as I
outlined in a recent post entitled,
"Oil "volatility"/"evaporation": The REAL story".

API SM-graded engine oils are refined to the point where volatiles that
might boil-off (above the standard) are removed during the manufacturing
process.

Oil and water don't mix, officially. Do you maybe mean that they form
emulsions with moisture?

<snip>

 

They absorb. Don't forget that even though they start with petroleum
based stock, they are highly modified and merged with a wide range of
monomers and chemicals during the polymerization process.

 

Some of which can actually soak up water, like vinyl?

 

Polyurethane, Polyamides (nylons), PET, Polycarbonate, Butyrate to
name a few. Some that don't absorb would be PVC, POM (delrin),
Polyethylene, Polypropylene. Of course any that do not absorb,
excessive surface moisture can be an issue due to condensation (cold
trucks/warm warehouse), so some processors may "dry" all materials, or
at least preheat them.

Most will absorb at a rate of about .1% per hour at 50% RH until they
reach an equilibrium. Saturation levels are usually at about .25% at
extremely high RH, though lowering ambient RH does not lower resin
moisture content.
Most manufacturers will usually specify a maximum for processing at
..03%, though that is usually in an industrial setting with high output
rates and the material is resident in the processing system for
seconds.

In the medical device arena, extremely small parts mean long residence
times (as much as 30 minutes or more), and the moisture levels
necessary directly correlate to residence times. I normally specify
..005% moisture for many processes, sometimes .000% to avoid hydrolysis
that may lead to reduced component integrity.

Of course, the above is only a brief summary.........I have had
discussions/debates with contemporaries that have lasted hours on the
best methods to achieve proper moisture levels for processing.

 

they most definitely can mix. there are many examples, but a simple
illustration is water and chloroform. they "don't mix", but actually
they do for binaries in small percentages, and in the presence of a
ternary, in this case acetic acid, they do in large percentages:

<http://www.standnes.no/chemix/images/scrshpic/acetic-acid-water-chloroform.gif>

there are loads of other examples. motor oil is far from being a simple
isomeric hydrocarbon.

 

Most drink containers are PET, PETE or PC. Oxygen/water transfer is
limited by the barrier coating (can't remember its composition just
now), but would the substrate actually /absorb/ water in the absence of
the barrier coating?

My trade mags tell me that Nestle has had technical challenges with its
supplier in its attempts to reduce the weight of its cold-fill plastic
bottles. Make the substrate thinner and weaker, and the barrier coating
is more difficult to make impermeable.

Hm. Vinyl seems to soak up water like crazy, to my observation. It turns
white and swells. The whiteness and swelling stops right at the
waterline.

PE is often used for food storage. It /appears/ affected not at all by
water, from what I can see.

Polypro floats, and also does not /seem/ to be affected by water.
Polypro is used extensively for the sort of pint and half-pint tubs used
when you buy potato- and macaroni-salads at the deli. These are, of
course, loaded with water.

And what about styrene? PS is ubiquitous in the single-serving
drink/pudding/yogurt/cereal market, usually in combination with
ultrasonically-sealed lids.

Never heard of that before. My industry has some dealings with food
processors. Plastic containers go straight from pallet to packing line,
and usually experience no preconditioning of any kind prior to packing,
other than a quick washing and drying. The drying is to remove surface
moisture, not the moisture inside the material.

For a gallon of motor oil, that would equate to about a third of an
ounce, or less than a quarter-teaspoon. You'd never see 1/4 TSP on a
dipstick.

 

208.90.168.18:

Sorry. A third of an ounce is 2 tsp, not 1/4 tsp.

I have an excuse: How often does one need to convert teaspoons to ounces?

 

Yes, they will absorb to their saturation level...but most drink
containers for carbonated drinks are either thicker or (most common)
uses a multilayer construction, sandwiching something like EVOH and a
polyamide. I believe the plastic beer bottles use up to 7 layers
(maybe more now) of PA-EVOH-PA-EVOH-PA, etc...as for an actual vapor
barrier coating, I'm not sure what is used for that, as industrial and
food packaging are not my area of expertise.

Just making the bottles thinner (from what I understand) was
challenging enough. Thin cross sections are prone to pinholes and
uneven strain sections. I would think that the material manufacturers
had to really tweak the resin formulation as well as advancements in
blow molding technology were used to allow the PET bottles to be as
thin as they are now.

PVC is polymerized with water. It doesn't usually absorb, and is used
for waterproofing things, as well as for water and drain pipes. Other
things can cause it to swell, such as pool chemicals (the reason why
chemical balancing of a pool is different based on if it uses a liner
or not) or if it is not UV stable. Higher temperatures can also cause
problems for softer grades. Of course once again, PVC is not my
forte' so to speak, as very little of it is used in medical devices.

Wikipedia has some good info on PVC
http://en.wikipedia.org/wiki/Polyvinyl_chloride

Pretty impervious to most things. Even used for underground gasoline
storage.

In general polypro and polyethylene have specific gravities of <1
(water is 1),

Styrene will absorb moisture to it's saturation point. It won't "drip
through", but it will absorb too much from ambient air to process
without drying.

Absorbed moisture needs to be driven out. Most engineering resins
specify a -40°c/f (the scales intersect at this point) in a desiccant
type system at a specific temperature. The air flow needs to go
through the pellets and be fairly well distributed, and the elevated
temp drives the moisture from the resin, and then the desiccant
absorbs it. Compressed air systems are used more frequently today as
well, as the capital investment is much less (no moving parts, no
regeneration or changing of desiccant).
There are some processors that use a hopper heater for surface
moisture on pellets, as well as to generate higher outputs.

I don't think that the absorption rate would apply directly to oil
itself, too many other factors involved. The thing about oil losing
moisture or evaporation is that the oil system in a vehicle is pretty
much a closed system (except for some pollution controls), so I would
have to believe there is a good chance most evaporation would be
re-absorbed.

 

Wouldn't that be 8 pinches....

 

I use individual.net
--

- dillon I am not invalid

Toby (Tri-Umph That's the Sweet Truth)
March 1998 - June 2010
What a dog. What a dog!