Oil, why not follow owner's manual recommendation?

[basia]

I am reading a 2010 Subaru owner's manual, it
shows a chart of recommended engine oil viscosities
for a given ambient temperature range. For cars
operating in temps above -5 degrees Fahrenheit
it recommends using 10w-30, 10w-40, or 10w-50 oils.

About 90% of US drivers fall into this category,
99.9% of the time.

Why is it that so many people decide not to follow
this recommendations and pour oils of 5w-30, or
5w-40 viscosities?

The manual shows a second chart where 5w-30,
and 5w-40 are shown along the entire temperature
spectrum, from less than -20 to above 100 degrees F.
Meaning these oils are also permissable, but they
are not a perfect match!

I do not understand the logic behind the use of these
thinner oils. Do people no longer care about their
engines, and prefer a thinner oil for better fuel efficiency
alone. Why then stop at 5w-30, and not pour 0w-30,
or 0w-20, or even thinner (0w-10 will soon be available).

Basia

 

[basia]

I am reading a 2010 Subaru owner's manual, it
shows a chart of recommended engine oil viscosities
for a given ambient temperature range.  For cars
operating in temps above -5 degrees Fahrenheit
it recommends using 10w-30, 10w-40, or 10w-50 oils.

About 90% of US drivers fall into this category,
99.9% of the time.

Why is it that so many people decide not to follow
this recommendations and pour oils of 5w-30, or
5w-40 viscosities?

The manual shows a second chart where 5w-30,
and 5w-40 are shown along the entire temperature
spectrum, from less than -20 to above 100 degrees F.
Meaning these oils are also permissable, but they
are not a perfect match!

I do not understand the logic behind the use of these
thinner oils.  Do people no longer care about their
engines, and prefer a thinner oil for better fuel efficiency
alone.   Why then stop at 5w-30, and not pour 0w-30,
or 0w-20, or even thinner (0w-10 will soon be available).

This is a 2010 Subaru Legacy owner's manual.

Basia

 

[AD]

I am reading a 2010 Subaru owner's manual, it
shows a chart of recommended engine oil viscosities
for a given ambient temperature range.  For cars
operating in temps above -5 degrees Fahrenheit
it recommends using 10w-30, 10w-40, or 10w-50 oils.

About 90% of US drivers fall into this category,
99.9% of the time.

Why is it that so many people decide not to follow
this recommendations and pour oils of 5w-30, or
5w-40 viscosities?

The manual shows a second chart where 5w-30,
and 5w-40 are shown along the entire temperature
spectrum, from less than -20 to above 100 degrees F.
Meaning these oils are also permissable, but they
are not a perfect match!

I do not understand the logic behind the use of these
thinner oils.  Do people no longer care about their
engines, and prefer a thinner oil for better fuel efficiency
alone.   Why then stop at 5w-30, and not pour 0w-30,
or 0w-20, or even thinner (0w-10 will soon be available).

The damage from 10w oil that does not flow on a rare day
when your claimed 10% of the population in snowbelt
drives their cars at -5F will outstrip the wear protection vs 5w
during warmer times.

FWIW mazda specifies 5w-20 for rx-8 and I would not be surprised if
some morons
ruined their wenkels with 10w-40. I suppose they would've been better
with 0w-20 you seem to have so much disdain for.

If I were in snowbelt or were a california skler type I'd stay away
from 10w
semisynthetic on a late model car in snowbelt Sept through May.
If you live in redneck states or run straight synthetic indeed 10w
could work just fine.

I run 75w-80 in the rear diff of my ancient RWD beater.
And that (dino) gear oil looks a lot like motor oil viscosity wise :^)

My car mechanic was delighted to pump this fluid: e-a-s-y

 

[Cameo]

I am reading a 2010 Subaru owner's manual, it
shows a chart of recommended engine oil viscosities
for a given ambient temperature range. For cars
operating in temps above -5 degrees Fahrenheit
it recommends using 10w-30, 10w-40, or 10w-50 oils.

About 90% of US drivers fall into this category,
99.9% of the time.

Why is it that so many people decide not to follow
this recommendations and pour oils of 5w-30, or
5w-40 viscosities?

My '94 Honda Accord Owner's Manual recommends 5W-30 oil, regardless of
the season.

 

[basia]

My '94 Honda Accord Owner's Manual recommends 5W-30 oil, regardless of
the season.

Honda is supposedly working on new oil viscosity
recommendation of 0w-10 !!!

Their chief chemist says the new upcoming engines are,
or will be designed to handle such. No word on longevity/durability.
I think they presume the public will believe it to be unaffected (?).

But how?

With such thin oil almost every start will be a cold start!

How else?

One of the reasons to use a somewhat thicker oil is
to have it cling better to internals and prevent cold starts.
This 0w-10 stuff is bound to drain into the pan entirely in
about an hour or so depending on ambient temperature.
A 10w-30 oil in 100 degree plus weather drains nearly
completely into the pan in just several hours, resulting
in a complete cold start!

I would never put anything thinner than 10w-30 in my
Subies engine, despite the fact that as horizontal engines
they don't drain oil completely into the pan.

Basia

 

[basia]

Honda is supposedly working on new oil viscosity
recommendation of 0w-10 !!!

Their chief chemist says the new upcoming engines are,
or will be designed to handle such.  No word on longevity/durability.
I think they presume the public will believe it to be unaffected (?).

But how?

With such thin oil almost every start will be a cold start!

How else?

One of the reasons to use a somewhat thicker oil is
to have it cling better to internals and prevent cold starts.
This 0w-10 stuff is bound to drain into the pan entirely in
about an hour or so depending on ambient temperature.
A 10w-30 oil in 100 degree plus weather drains nearly
completely into the pan in just several hours, resulting
in a complete cold start!

I forgot to add, depending on how frequently
you drive you want an oil that cover the internals
until you start the engine next time.

If it is a daily driver, and in cool weather,
a 5w-30 might do the job, i.e. not drain into
the pan entirely in 12 hours or so. If the car
is driven only a few days a week, a 10w-30,
or 15w-40 is better. During hot weather
a 20w-50 is much better. If the car is driven
ocassionally, say once or twice a month,
its a good idea to use a straight 30. It'll
cling to parts for a long time preventing rust
and a complet cold start even after days.

A complete cold start is when the engine gets
worn most.

Basia

 

[1 Lucky Texan]

Honda is supposedly working on new oil viscosity
recommendation of 0w-10 !!!

Their chief chemist says the new upcoming engines are,
or will be designed to handle such.  No word on longevity/durability.
I think they presume the public will believe it to be unaffected (?).

But how?

With such thin oil almost every start will be a cold start!

How else?

One of the reasons to use a somewhat thicker oil is
to have it cling better to internals and prevent cold starts.
This 0w-10 stuff is bound to drain into the pan entirely in
about an hour or so depending on ambient temperature.
A 10w-30 oil in 100 degree plus weather drains nearly
completely into the pan in just several hours, resulting
in a complete cold start!

I would never put anything thinner than 10w-30 in my
Subies engine, despite the fact that as horizontal engines
they don't drain oil completely into the pan.

Basia

I think tighter clearances demand lower viscosities. Perhaps with CAD,
modern alloys and modern machining, they can achieve design parameters
that work better with lower viscosities.

 

[John]

I am reading a 2010 Subaru owner's manual, it
shows a chart of recommended engine oil viscosities
for a given ambient temperature range. For cars
operating in temps above -5 degrees Fahrenheit
it recommends using 10w-30, 10w-40, or 10w-50 oils.

About 90% of US drivers fall into this category,
99.9% of the time.

Why is it that so many people decide not to follow
this recommendations and pour oils of 5w-30, or
5w-40 viscosities?

The manual shows a second chart where 5w-30,
and 5w-40 are shown along the entire temperature
spectrum, from less than -20 to above 100 degrees F.
Meaning these oils are also permissable, but they
are not a perfect match!

I do not understand the logic behind the use of these
thinner oils. Do people no longer care about their
engines, and prefer a thinner oil for better fuel efficiency
alone. Why then stop at 5w-30, and not pour 0w-30,
or 0w-20, or even thinner (0w-10 will soon be available).

Basia

I don't understand what your point is about using a thinner oil if the
manual states 5w is fine for -20 to +100F. You just answered your own
question.
Personally, there's no way I'm having a 10w oil in when it is anywhere
below 20F. I can certainly hear the difference on start-up
For your question about 0w-30 or 0w-20, the manual does not state to use
it, so....why would you? Moot point

 

[clare]

I think tighter clearances demand lower viscosities. Perhaps with CAD,
modern alloys and modern machining, they can achieve design parameters
that work better with lower viscosities.

The specified clearances have not changed any significant amount in
the last 30 years.

 

[clare]

I don't understand what your point is about using a thinner oil if the
manual states 5w is fine for -20 to +100F. You just answered your own
question.
Personally, there's no way I'm having a 10w oil in when it is anywhere
below 20F. I can certainly hear the difference on start-up
For your question about 0w-30 or 0w-20, the manual does not state to use
it, so....why would you? Moot point

I have ALWAYS used a minimum of base 10w oils in all my cars here in
Ontario Canada. My current vehicle uses 10W40 Synthetic - but
everything else I've ever owned used 10W40 standard oil in cold
weather and 20W50 in summer.

 

[basia]

I don't understand what your point is about using a thinner oil if the
manual states 5w is fine for -20 to +100F.  You just answered your own
question.
Personally, there's no way I'm having a 10w oil in when it is anywhere
below 20F.  I can certainly hear the difference on start-up
For your question about 0w-30 or 0w-20, the manual does not state to use
it, so....why would you?  Moot point

You are very logical, but the manual shows
two charts, one specifies three viscosity grades
which are progressively thicker and aligned with
rising temperatures, and looks something like this:

-5F ----->10w-30, 10w-40, 10w-50

....the other shows only two thinner grades
along the entire temperature spectrum, and looks
like this:

-20F <---- 5w-30, 5w-40 ----> 100F


Why two different recommendations?

Both 5w-40, and 10w-50 cannot protect
exactly the same way. One must be
better/worse in some aspects than the other.

What is the point of recommending two different
grades for same operating conditions?????

To stir up confusion?

Or is it perhaps because manufacturers are being
pushed into recommending fuel conserving oil grades,
but cannot easily abandon the idea that slightly
thicker oils protect the machinery far better?

I suspect that is exactly the case!

Basia

 

[basia]

 The specified clearances have not changed any significant amount in
the last 30 years.

They may be a bit tighter nowadays, but not by very much.
The Subie 2.5L engine specifications I think are the same
for more than a decade.

But, once you accept the arguments for thinner oil,
and start using a ultra-thin oil that does little or nothing
to prevent cold starts (because it drains into the pan
too fast),

....the logic changes into one favoring progressively
thinner oils, as these flow better and the pump can
push them faster to were the oil needs to be.

Basia

 

[basia]

The specified clearances have not changed any significant amount in
the last 30 years.

They may be a bit tighter nowadays, but not by very much.
The Subie 2.5L engine specifications I think are the same
for more than a decade.

But, once you accept the arguments for thinner oil
(better cooling, fuel efficiency) and start using a ultra-thin
oil that does little or nothing to prevent cold starts (because
it drains into the pan too fast),

....the logic changes into one favoring progressively
thinner oils, as these flow better and the pump can
push them faster to were the oil needs to be.

Basia

 

[John]

They may be a bit tighter nowadays, but not by very much.
The Subie 2.5L engine specifications I think are the same
for more than a decade.

But, once you accept the arguments for thinner oil,
and start using a ultra-thin oil that does little or nothing
to prevent cold starts (because it drains into the pan
too fast),

...the logic changes into one favoring progressively
thinner oils, as these flow better and the pump can
push them faster to were the oil needs to be.

Basia

Asside from tight tolerances, I thought the idea of a thinner oil,
especially at colder temps, was to get the flow moving more freely vs.
the thicker weight possibly not flowing as quickly and thus causing
limited oil starvation on startup.

 

[clare]

They may be a bit tighter nowadays, but not by very much.
The Subie 2.5L engine specifications I think are the same
for more than a decade.

But, once you accept the arguments for thinner oil,
and start using a ultra-thin oil that does little or nothing
to prevent cold starts (because it drains into the pan
too fast),

...the logic changes into one favoring progressively
thinner oils, as these flow better and the pump can
push them faster to were the oil needs to be.

Basia

The "theory" is that thin oil pumps faster, so the "dry start" doesn't
last as long. Personally, I'm not sure I buy it. I still like an oil
with a bit of body to it.

 

[1 Lucky Texan]

You are very logical, but the manual shows
two charts, one specifies three viscosity grades
which are progressively thicker and aligned with
rising temperatures, and looks something like this:

-5F ----->10w-30, 10w-40, 10w-50

...the other shows only two thinner grades
along the entire temperature spectrum, and looks
like this:

-20F <---- 5w-30, 5w-40 ----> 100F

Why two different recommendations?

Both 5w-40, and 10w-50 cannot protect
exactly the same way.  One must be
better/worse in some aspects than the other.

What is the point of recommending two different
grades for same operating conditions?????

To stir up confusion?

Or is it perhaps because manufacturers are being
pushed into recommending fuel conserving oil grades,
but cannot easily abandon the idea that slightly
thicker oils protect the machinery far better?

I suspect that is exactly the case!

Basia

I occasionally read rumors of owner's manuals in other countries,
without CAFE-type regulations, recommending higher vis. oil for the
same engines sold in the States where the 5w-w'ever range is
recommended. Any way to confirm this?

 

[basia]

I occasionally read rumors of owner's manuals in other countries,
without CAFE-type regulations, recommending higher vis. oil for the
same engines sold in the States where the 5w-w'ever range is
recommended. Any way to confirm this?

I can't find seem to find any Polish Subaru
owner's manuals online. There are some
abbreviated versions but they don't go into
oil recommendations.

Basia

 

[AD]

I occasionally read rumors of owner's manuals in other countries,
without CAFE-type regulations, recommending higher vis. oil for the
same engines sold in the States where the 5w-w'ever range is
recommended. Any way to confirm this?

Carl,
the repair shops here use translated Haynes, I checked )))))

Most people (here) run 10w-40 for some reason. probably because
most of the cars on the road have high mileage and the tolerances
on a 120k+ miler are not what they used to be on the maiden voyage of
the car

I guess 10w40 flows some but I don't give a shit. 5w-30 flows better
in local (cold)
winter and the engine does not have to push thick sludge around. But,
then,
it's a beater. Still, I'll run 5w30 when my A4 arrives.

I run 20w-50 in my bikes when I lived in bloody hot kaulifornia
though.
10w-40 in cars since skiing trips were rare.

Is that viscosity-vs-temperature chart so difficult to grasp in adjust
to your area temperature ranges?

Also if you leave in the bloody hot sunbelt why the heck do you need
subaru to begin with?
Get a rear wheel driver, pour your favorite 20w50 in it and have fun.

 

[bugalugs]

I occasionally read rumors of owner's manuals in other countries,
without CAFE-type regulations, recommending higher vis. oil for the
same engines sold in the States where the 5w-w'ever range is
recommended. Any way to confirm this?

Here in New Zealand the owners manual for my 02 GT Legacy (twin turbo)
recommends SG 10W-30,SH 10W-30, SJ 5W-30 The car was built in Japan and
the manual is a translation of the manual for a JDM.

I run Castrol Magnatec which is 10w 40.

 

[clare]

I occasionally read rumors of owner's manuals in other countries,
without CAFE-type regulations, recommending higher vis. oil for the
same engines sold in the States where the 5w-w'ever range is
recommended. Any way to confirm this?

It IS true. When I was in Burkina a number of years back, NOTHING
recommended anything thinner than 10W40 - but then again it was HOT
over there. 15W40 and 20W50 were very common.