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Car Forum / Porsche / Porsche Cars / March 2005

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1989 Porsche 928 S4: what oil at 100K?

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F. Baker - 09 Mar 2005 01:22 GMT
What grade of oil would one use in a 1989
Porsche 928 S4, automatic transmission, 100K?
I say Mobil-1 "extended performance" synthetic
15W-50 is the best bet, though the opinions
vary on this widely.  The "extended performance"
synthetic that Mobil-1 has is (at the moment)
hard to find; does anyone know where it can
be found online?

Is 10W-40 too thin for the 928?  Reading misc
websites I've seen people recommend from 5W-30
to 20W-50, so I'm understandably a bit lost on
the issue of grade.  But at 100K, I personally
lean towards the thicker oils.

I will be (likely) purchasing this exact car shortly.
Is the Fram (PH6583) oil filter acceptable for use
in this car?  It supposedly is, though the other
(foreign-manufactured) OFs seem to be much larger.
This car requires 9 quarts of motor oil, am I right?
The Fram PH6583 seems too small.   K&N doesn't make
an oil filter (that I'm aware of) that fits this
car; what manufacturer/model would be best so far
as oil filters are concerned?

Also: Is synthetic ATF a good option for use in
a car of this age/miles?  Mobil-1 sells one, though
I don't hear nearly as much talk about synthetic
ATF as synthetic motor oils.  Are they of any
conceivable advantage?
Bernard farquart - 09 Mar 2005 03:28 GMT
> What grade of oil would one use in a 1989
> Porsche 928 S4, automatic transmission, 100K?
[quoted text clipped - 4 lines]
> hard to find; does anyone know where it can
> be found online?

The "Extended Performance" 15w50 is just the new version
of Mobil1. It is rolling out slowly. I work in an auto parts retail
and it took a few weeks after we ran out of the old stuff to get the
new stuff in. It is in now, however.

> Is 10W-40 too thin for the 928?  Reading misc
> websites I've seen people recommend from 5W-30
> to 20W-50, so I'm understandably a bit lost on
> the issue of grade.  But at 100K, I personally
> lean towards the thicker oils.

I have had an '84 928 with 200k + miles and use the
15w50, I have very little oil usage, and go about
5000 to 6000 miles between oil changes. I recommend
you get the Mann filter or a Mahle if you can find it.
I have personally had a Napa Gold filter blow off
of my 914 when I had it, due to poorly cut threads
on the (supposedly) top of the line Napa filter.
I have seen fram filters "popped" out with the seam
split around the base (total engine oil loss)

I figure the three bucks extra I spend above the cost
of the fram means very little compared to the cost of the
oil I run. Not to mention the engine.

> I will be (likely) purchasing this exact car shortly.
> Is the Fram (PH6583) oil filter acceptable for use
[quoted text clipped - 11 lines]
> ATF as synthetic motor oils.  Are they of any
> conceivable advantage?

Synthetic oils (and trans fluid) will not break down
due to heat like standard, so they are a better bet,
just don't start playing areound with non specified
*types* of fluids and you should be fine.

Bernard
scott.mark@gmail.com - 09 Mar 2005 16:15 GMT
Go here!
Many thanks to Doug Hillary for this article. I believe it explains
every thing you might need to know on lubricants for the 928. It is to
be found at the below "Land Shark Oz site.
http://www.landsharkoz.com/tt/ttlubricant.htm

Mark
G. Patricks - 09 Mar 2005 15:14 GMT
You may want to take a look here regarding Oil Filters..
http://minimopar.knizefamily.net/oilfilters.html
I would either use OEM or a Pureolater Pure One (if you can find it).

GP

>Is the Fram (PH6583) oil filter acceptable for use
>in this car?  It supposedly is, though the other
>(foreign-manufactured) OFs seem to be much larger.
>This car requires 9 quarts of motor oil, am I right?
>The Fram PH6583 seems too small.  
Steve - 10 Mar 2005 00:16 GMT
> What grade of oil would one use in a 1989
> Porsche 928 S4, automatic transmission, 100K?
> I say Mobil-1 "extended performance" synthetic
> 15W-50 is the best bet, though the opinions
> vary on this widely.

What grade does the owners manual recommend for the climate that you
drive the car in? Whatever that grade is, I'd use it.

> The "extended performance"
> synthetic that Mobil-1 has is (at the moment)

The "extended performance" is just a re-labelling of good ol' Mobil 1.
If its not available yet, do your next change with the correct grade of
Mobil 1.

> Is 10W-40 too thin for the 928?  Reading misc
> websites I've seen people recommend from 5W-30
> to 20W-50, so I'm understandably a bit lost on
> the issue of grade.  But at 100K, I personally
> lean towards the thicker oils.

First off, most engines aren't super picky about grade, so they'll live
happily on a pretty wide range of grades. The optimum balance of engine
protection without being so thick as to waste power is what really
determines the "best" grade. Thicker oil doesn't necessarily translate
to "better protection" if the engine maintains enough oil pressure on
thinner oil. In fact, thinner oils tend to get pumped more evenly
throughout the engine, and circulate faster through the engine and thus
provide a bit better cooling for the oil-cooled components (like the
undersides of the pistons).

Secondly, 100k is NOT a lot of miles for a liquid-cooled v8. If its
still got good compression, good balance of compression, low or no oil
consumption, and good oil pressure, use the grade that is recommended by
the manufacturer. I've got 4 different engines (1 Chrysler v6, three
older Chrysler v8s), 3 with over 200,000 miles on the clock and 1 with
160,000, and I run Mobil-1 10w30 in all, which happens to be the
recommended grade for them all. They all maintain good oil pressure at
hot idle, and that's the point where oil pressure will fall too low if
an engine's clearances have opened up too wide for the recommended grade.

> I will be (likely) purchasing this exact car shortly.
> Is the Fram (PH6583) oil filter acceptable for use
> in this car?  

I wouldn't run a Fram on a sewage pump, myself. Wix and Purolator make
some of the better filters on the market. The Mobil 1 branded filter is
also very good, although I think its a bit overpriced and I don't know
if its available for that car.

> Also: Is synthetic ATF a good option for use in
> a car of this age/miles?  Mobil-1 sells one, though
> I don't hear nearly as much talk about synthetic
> ATF as synthetic motor oils.  Are they of any
> conceivable advantage?

Not much. ATF is far more stable and lives in a far more forgiving
environment (no combustion by-products continually injected into it)
than engine oil. IIRC, the 928 automatic uses good old Dexron-III just
like Chrysler and GM did in the 80s. If you want a little extra
insurance at more than twice the price, use Mobil-1 synthetic ATF.
Otherwise, use a name-brand and follow the service schedule.
y_p_w - 14 Mar 2005 22:03 GMT
> > What grade of oil would one use in a 1989
> > Porsche 928 S4, automatic transmission, 100K?
[quoted text clipped - 11 lines]
> If its not available yet, do your next change with the correct grade of
> Mobil 1.

It's more than just a relabelled product.  Whether or not it's a
good idea for most car owners these days is debatable.  They seem
to have picked a market niche for the "regular" Mobil 1 and the
"Extended Performance".  The regular version comes in the 5W-30/
10W-30 weights that most manufacturers recommend these days, and
0W-40 which is supposedly for many European cars.  There's also
the 0W-30 which I believe GM recommends for cold climates.  I saw
the first three at a local Wal-Mart.

The "Extended Performance" version also seems to come in the 10W-40
and 15W-50 weights that a lot of DIY owners like to use.  I saw the
new "EP" Mobil 1, and the kicker is that none of them carry the API
"Starburst" or "Energy Conserving" labels.  They also only come with
the API SL standard while the regular Mobil 1 now has the newer API
SM.

> > Is 10W-40 too thin for the 928?  Reading misc
> > websites I've seen people recommend from 5W-30
[quoted text clipped - 7 lines]
> determines the "best" grade. Thicker oil doesn't necessarily translate
> to "better protection" if the engine maintains enough oil pressure on

> thinner oil. In fact, thinner oils tend to get pumped more evenly
> throughout the engine, and circulate faster through the engine and thus
> provide a bit better cooling for the oil-cooled components (like the
> undersides of the pistons).

True.  There are so many people who were convinced that 20W-50
had to protect better because it was thicker.  The likely thing
that might happen is a small power loss due to internal drag, and
worse fuel economy.

> Secondly, 100k is NOT a lot of miles for a liquid-cooled v8. If its
> still got good compression, good balance of compression, low or no oil
[quoted text clipped - 14 lines]
> also very good, although I think its a bit overpriced and I don't know
> if its available for that car.

The Mobil 1 filter is made by a contractor called Champion Labs.  They
make filters sold under any number of brand names.  Some of them are
OEM, house labels, etc.  Many of their products are very good.

> > Also: Is synthetic ATF a good option for use in
> > a car of this age/miles?  Mobil-1 sells one, though
[quoted text clipped - 8 lines]
> insurance at more than twice the price, use Mobil-1 synthetic ATF.
> Otherwise, use a name-brand and follow the service schedule.

It would have been Dexron-II back then.  I wouldn't recommend following
some of the extremely high service intervals these days (i.e. never
change the transmission fluid).
Steve - 16 Mar 2005 01:04 GMT
>>>What grade of oil would one use in a 1989
>>>Porsche 928 S4, automatic transmission, 100K?
[quoted text clipped - 26 lines]
> the 0W-30 which I believe GM recommends for cold climates.  I saw
> the first three at a local Wal-Mart.

I should have said a "replacement" product. Mobil-1 has now been
replaced by Mobil-1 "Extended Performance" and (maybe) reformulated a
little bit. If you look at the other oils (Mobil Clean 5000 and Mobil
Clean 7500), They are replacements for Mobil's line of non-synthetic (MC
5000) and synthetic blend (MC 7500) oils. Mobil-1 extended performance
is the only "real Mobil-1" fully synthetic oil.

See:
http://www.mobiloil.com/USA-English/MotorOil/Home/Homepage.aspx
y_p_w - 16 Mar 2005 01:47 GMT
> >>>What grade of oil would one use in a 1989
> >>>Porsche 928 S4, automatic transmission, 100K?
[quoted text clipped - 29 lines]
> I should have said a "replacement" product. Mobil-1 has now been
> replaced by Mobil-1 "Extended Performance" and (maybe) reformulated a

> little bit. If you look at the other oils (Mobil Clean 5000 and Mobil

> Clean 7500), They are replacements for Mobil's line of non-synthetic (MC
> 5000) and synthetic blend (MC 7500) oils. Mobil-1 extended performance
> is the only "real Mobil-1" fully synthetic oil.
>
> See:
> http://www.mobiloil.com/USA-English/MotorOil/Home/Homepage.aspx

They still have the original "Mobil 1" lineup.  I didn't give the
full set of what they now offer.  It's, 0W-30, 0W-40, 5W-20 (for
Ford/Honda/Mazda), 5W-30, and 10W-30.  The 0W-40 is what Porsche
would recommend, and it's close to the European Mobil 1 5W-40 from
the factory.  The 0W-40 is also supposed to meet the Mercedes Benz
229.5 standard for extended-drain oils, and it's not part of the
Mobil 1 "Extended Performance" line.

I'm still not sure what's completely up with Mobil 1 Extended
Performance.  By going to the earlier API standard (SL) they can't
use an "Energy Conserving" label - it's likely some sort of
burecratic thing.  I'm not terribly convinced that using one of
these "extended drain" oils is better than regular Mobil 1 changed
more often.  Boosted additives often means less lubricating oil.
Steve - 16 Mar 2005 18:44 GMT
> full set of what they now offer.  It's, 0W-30, 0W-40, 5W-20 (for
> Ford/Honda/Mazda), 5W-30, and 10W-30.  The 0W-40 is what Porsche
> would recommend,

They might *now*, but when the 928S4 was built, there was no such oil.

> I'm still not sure what's completely up with Mobil 1 Extended
> Performance.  By going to the earlier API standard (SL) they can't
> use an "Energy Conserving" label

The API is notorious for occasionally *limiting* the amount of various
additives that are "acceptable" for a given standard (SJ, SL, etc.)
usually under the guise of wanting to limit chemicals that might poison
catalytic convertors. Sometimes this has a very negative effect on the
lubricating qualities of the oil- some of the limited additives are
excellent extreme-pressure wear inhibitors (zinc) and others are
excellent pH stabilizers that keep the TBN low during long drain
intervals (one of these changes led to Mobil coming out with the
"tri-synthetic" Mobil 1 a few years ago, which turned out to be pretty
crappy oil compared to the previous and subsequent versions when API
backed off on the requirement for their next standard).  I haven't
researched this particular case, but it may be one of those instances
where Mobil feels that they can produce a better long-life oil with
better long-term TBN under the SL standard than they can under the
current standards. Given that the Mobil site flat-out states that
"extended performance" contains "50% more SuperSyn,36 percent more
anti-wear additives, and 37 percent more cleaning agents than the
current Mobil 1," I would guess that it simply contains too much of one
or more components to qualify for the newer rating.
Daniel J. Stern - 16 Mar 2005 19:30 GMT
> > I'm still not sure what's completely up with Mobil 1 Extended
> > Performance.  By going to the earlier API standard (SL) they can't use
> > an "Energy Conserving" label

> The API is notorious for occasionally *limiting* the amount of various
> additives that are "acceptable" for a given standard (SJ, SL, etc.)
[quoted text clipped - 15 lines]
> current Mobil 1," I would guess that it simply contains too much of one
> or more components to qualify for the newer rating.

TBN?
Steve - 16 Mar 2005 19:56 GMT
>>>I'm still not sure what's completely up with Mobil 1 Extended
>>>Performance.  By going to the earlier API standard (SL) they can't use
[quoted text clipped - 21 lines]
>
> TBN?

Total base number- a measure of how well the oil is resisting acid
formation during extended use, and one of the most critical parameters
to look at when you are using oil analyses to tell you when to change
the oil instead of just using the calendar or odometer.
y_p_w - 16 Mar 2005 23:26 GMT
> > full set of what they now offer.  It's, 0W-30, 0W-40, 5W-20 (for
> > Ford/Honda/Mazda), 5W-30, and 10W-30.  The 0W-40 is what Porsche
> > would recommend,
>
> They might *now*, but when the 928S4 was built, there was no such
> oil.

Of course I'm referring to Porsche's current list.  When Porsche
first started recommending Mobil 1, there were bulletins saying
that they approved of all weights of Mobil 1 depending on ambient
conditions or usage.  It was probably not a great idea.

<http://www.alldata.com/tsb/Porsche/1089356400000_1093417200000_12-04/index.html0>
<http://www.alldata.com/tsb/Porsche/1089442800000_1093417200000_13-04/index.html>

Of all these oils, only Mobil 1 0W-40 is the one I've seen on store
shelves.  A shop I've used does stock Kendall Synthetic 5W-40 though.

> > I'm still not sure what's completely up with Mobil 1 Extended
> > Performance.  By going to the earlier API standard (SL) they can't
[quoted text clipped - 12 lines]
> subsequent versions when API backed off on the requirement for their
> next standard).

I thought ZDDP was considered and antiwear additive, and that "extreme
pressure" usually referred to the (mostly sulfer compound) additives
used in gear oil.  IIRC, these EP additives aren't well suited in
motor oil because they wouldn't survive the higher temps.

> I haven't
> researched this particular case, but it may be one of those instances
[quoted text clipped - 5 lines]
> current Mobil 1," I would guess that it simply contains too much of
> one or more components to qualify for the newer rating.

That's what I was guessing too.  However - they seem to be targeting
this series at the car well beyond its warranty period.  The car well
beyond its warranty period is probably not going to have a factory
recommendation beyond API SL anyways.  Not that this matters with
Porsche, which comes up with a list of approved oils, and of which
(regular) Mobil 1 0W-40 is on the list.
Steve - 17 Mar 2005 21:22 GMT
>>>full set of what they now offer.  It's, 0W-30, 0W-40, 5W-20 (for
>>>Ford/Honda/Mazda), 5W-30, and 10W-30.  The 0W-40 is what Porsche
[quoted text clipped - 13 lines]
> Of all these oils, only Mobil 1 0W-40 is the one I've seen on store
> shelves.  A shop I've used does stock Kendall Synthetic 5W-40 though.

I looked, and I notice that they don't recommend any xW-30 or xW-20
oils... then I noticed the earlier page that referred to the Boxster
engine ;-)

Air-coolers have different needs.... :-)

>>>I'm still not sure what's completely up with Mobil 1 Extended
>>>Performance.  By going to the earlier API standard (SL) they can't
[quoted text clipped - 17 lines]
> used in gear oil.  IIRC, these EP additives aren't well suited in
> motor oil because they wouldn't survive the higher temps.

You're probably right on the extreme pressure terminology. I was
specifically referring to sacrifical additives (of which ZDP is one)
that are effective under high-pressure, direct metal-to-metal contact
that exceeds the film strength of the base lubricant. I was using
"extreme pressure" in the generic, not the specific.

> That's what I was guessing too.  However - they seem to be targeting
> this series at the car well beyond its warranty period.  The car well
> beyond its warranty period is probably not going to have a factory
> recommendation beyond API SL anyways.

Which is FINE with me- all the cars I care about keeping forever are
WELL beyond their warranty period! New cars are boring :-p

This has come up on another thread on rec.autos.tech as well, and
resulted in a link to some comments made by a GM engineer at:

http://cadillacforums.com/forums/showthread.php?t=32413&page=1&pp=20

If you plow through all the commentary and facts and replies (by the
way, he believes any API-rated oil is just fine in the Northstar),
you'll come to one point where he says that he wouldn't hesitate to run
a Northstar right up to the built-in oil-life monitor's 12,500 mile
limit, but would never do the same with an HT4100 because it has flat
tappets, a gear-driven distributor, gear-type oil pump, and a non-roller
timing chain, all of which eat up the ZDP additives in an oil much
faster than all the other engine parts common to both engine designs
(bearings, cylinder-to-piston friction, etc).

SO- if you ARE interested in taking the best possible care of an older
engine that does have any of these features (mine all only share the
flat tappets and distributor drive gear, because Chrysler v8s have
always used gerotor oil pumps and I've got roller timing chains on them
all), then an oil with a higher dose of ZDP is probably a very good
thing to use, even if you don't run it to extremely high milage.

So i'll probably start using Mobil 1 Extended Life, but I'll still
change it at around 7000 to 9000 miles, just like I've done for the last
15 years or so.
y_p_w - 17 Mar 2005 22:20 GMT
> This has come up on another thread on rec.autos.tech as well, and
> resulted in a link to some comments made by a GM engineer at:
[quoted text clipped - 6 lines]
> a Northstar right up to the built-in oil-life monitor's 12,500 mile
> limit, but would never do the same with an HT4100 because it has flat

> tappets, a gear-driven distributor, gear-type oil pump, and a non-roller
> timing chain, all of which eat up the ZDP additives in an oil much
> faster than all the other engine parts common to both engine designs
> (bearings, cylinder-to-piston friction, etc).

I've gone through that thread and he seems to be quite knowledgeable.
However - I seem to recall that GM has recommended 0W-30 synthetic
oil for those who run their cars in extremely cold climates.  I read
through the owner's manual for my dad's '96 Buick Regal, and even that
recommends a synthetic 5W-30 below a certain temp (although the
definition of "synthetic oil" was clearer then than now).  That car
came with rather specific recommendations that on 10W-30 be used if
above freezing, while 5W-30 should only be used if less than 50 deg F.

> SO- if you ARE interested in taking the best possible care of an older
> engine that does have any of these features (mine all only share the
> flat tappets and distributor drive gear, because Chrysler v8s have
> always used gerotor oil pumps and I've got roller timing chains on them
> all), then an oil with a higher dose of ZDP is probably a very good
> thing to use, even if you don't run it to extremely high milage.

I thought the big thing with ZDDP is that it fouls catalytic
converters.  There was some controversy that in the switch from the
API SH to SJ standard, the result may have been an overall lowering
of antiwear properties.  The concern wasn't that the minimum antiwear
standard went down from SH to SJ.  Oil formulas included quantities of
ZDDP that exceeded antiwear requirements, but supposedly the mandate
to reduce zinc and phosphorous lowered the amount of ZDDP that could
be used.

> So i'll probably start using Mobil 1 Extended Life, but I'll still
> change it at around 7000 to 9000 miles, just like I've done for the last
> 15 years or so.

I didn't look closely on the shelf at Wally World, but it didn't seem
that they charged a premium for it over regular Mobil 1.
Steve - 17 Mar 2005 22:40 GMT
> I didn't look closely on the shelf at Wally World, but it didn't seem
> that they charged a premium for it over regular Mobil 1.

IIRC, it was exactly the same price at Schlep Boyz.
y_p_w - 25 Mar 2005 17:37 GMT
> > I didn't look closely on the shelf at Wally World, but it didn't seem
> > that they charged a premium for it over regular Mobil 1.
>
> IIRC, it was exactly the same price at Schlep Boyz.

I looked again.  Granted each Wal-Mart sets it prices differently, but
the one I went to had "regular" Mobil 1 at $4.32/quart and $18.92
for a 5 quart jug.  The "Extended Performance" was $5.40/quart
and $24 for a 5 quart jug.
 
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