Fastest928

please check out:

<a href="http://www.memagazine.org/backissues/may99/features/vitalsigns/vitalsigns.html" target="_blank">http://www.memagazine.org/backissues/may99/features/vitalsigns/vitalsigns.html</a>

Need less to say, I diagree that your methodology for determining oil interval changes has any validity...Doug, at least you are on the right path and understand the driving conditions of your vehicles, however, unless you tested the oil at new, and subsequently every 10K or so, you really have no idea how much wear has occurred.

Read this and you might change your opinions...want more info on the "change more often can't hurt, can only help" laymans position?

Jim, look at the part about water vapor in the crankcase...I think you will find it intersting.

Any tribologists on the list?

Marc

Good Luck
Marc

Fastest928

oops, here is another atricle by cummings...I think they know a bit about industrial diesels and lubrication.....

<a href="http://www.caterpillar.com/products/shared/marine/pleasure_craft/product_support/docs/OIL.DOC" target="_blank">http://www.caterpillar.com/products/shared/marine/pleasure_craft/product_support/docs/OIL.DOC</a>

have fun,
marc

T_MaX

When in the market for a 928, I was told by all the pros that a bit of oil consumption in a GTS was normal and was due to the previously listed facts. I just wander how many GTS owners change their oil before 3-5K and how many change it at 15K?

Oil brands, it has been my experiance that when the hype is striped away, there is only a few oil MFG. that are offering a truly superior product.

Moisture in motor oil is very common. Every time a hot engine is shut-down and left to cool it will such in water ladened air (humidity) from any open port (no matter the size). It has been my experiance, motors that are run (a standing idle) just enough to warm-up than shut-down will have the most moisture. However an engine in a car that is driven (not a standing idle) for at least 45 min. or more, will burn off most acummulated moisture no matter how hummid it is.

Comparing oil requirements/recommendations of a Gas engine to the same of a Diesel is an apple and orange argument.

1. Large diesel engines operate in a much lower RPM range for a longer period.
2. The Diesel fuel is used as a lubricant.
3. Most large diesel engines have removable side pannels bolted to the side of the blocks so the entire interior of the block can be cleaned during a major oil change ( Cat D398 (V12) every 600 hours).
4. The properties, quality and additves in Diesel and Gas are very differant and after combustion do differant things to the oil.
5. When its time to rebuild that diesel, you can order new cylinders that press in with your new pistons for just a few more duckies.

Fastest928

Randall,
Good wisdom!

Best wishes,
marc

Gary Quayle

Just for the record Caterpillar and Cummins are two different companies. The correct spelling is Cummins. My friends, who drive Dodge pickups with Cummins diesels, wouldn't appreciate the confusion.

Fastest928

Thanks for the correction Gary..it was late!

Marc

Randy V

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Jim bailey - 928 International:
<strong> Tying a rope to a pig "helps prevent pigs from flying" but does not prove that pigs can fly.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Hilarious analogy Jim <img border="0" alt="[hiha]" title="" src="graemlins/roflmao.gif" /> !

Doug Hillary

Marc & Randall,
Marc,
Your comments amaze me " on the right path"!. My initial oil testing was done for Castrol Oil Australia during the 1980s, over three years, with Castrol R Synthetic 10w-60 - a petrol/diesel SL/CD A3 spec oil (now ). Later on another Castrol project in the early 1990s with a protype synthetic CG/CH diesel oil. Since 1998 I have worked with Esso Mobil Oil Australia using Mobil Delvac 1 ( a fully synthetic SJ-CH4 spec oil and well recommended for both diesel and petrol engines )over many millions of kms.

Of course new oil is the basis for any analysis but the most important of all is engine maker/oil maker and USER experience. The new oil only tells part of the story

Yes, we sampled at 20k km intervals initially moving quickly to 40k km intervals. I have analysed hundreds of samples over the last 25 years! And still do!

We random sample our oils now but usually around 50k km and 70k km to detect any ABNORMAL increase in wear metals, an increase/decrease in viscosity, silicates, a raising of the soot levels ( diesel engine specific - we use a Glacier centrifuge on each engine to collect soot - "take up" rate is .003g/km and centrifuge capacity 600g ) but mainly for a lowering of the oil's Total Base Number (TBN). The various parameters are set by the engine maker and agreed with the oil maker. User experience plays a huge part here - ask any engine maker
We keep very detailed computer records on each engine ( oil samples analysis, repairs etc. ) collectively covering many millions of kilometers.
Yes the qualities of petrol and diesel engine oils are different. Since API spec SG, all petrol oils have to meet at least CC diesel spec and most meet CD or CF - the latest is CH4.
In the 1950s and 1960s both Benz and Porsche recommeded a Series 3 Cat, MIL-L2104A/A supp1/B spec diesel engine oil!
These worked best in VWs too - reducing sludge
Randall,
In disputing some of your "details" please note:
1 - yes some operate at 1500-1700rpm/100km/h others up to 2000-2500rpm/100km/h. ( My MY89 928S4 does about 2100rpm/100km/h
2 - Diesel fuel is only a lubricant to injectors and fuel pumps. It is NEVER viewed as a lubricant when mixed with engine oil. It has a high sulphur content too. It can be a source of crankcase oil dilution which will require urgent changing
3 - No modern Trucking diesel engine that I know of has "removable side panels" for cleaning. Sludged engines are initially cleaned by rapid oil changes or if this fails in a sililar way to petrol engines! Incorrect oil spec. is the main problem causing internal deposits - just like in a petrol engine
4 - Agreed, Diesel and Petrol combustion byproducts are different. Oils are formulated to handle both - read the oil spec label!!! They have been API required since at least since 1989
5 - I cannot believe this statement. Yes all modern diesels use liners. The cost of a new 500hp Detroit diesel here is about $40000. Reconditioning about $20000 depending on what is done - " a few more duckies" than what??. Some cars use liners too
Summary
I have used synthetic oils in various engines over the last nearly 30 years. Some basic sense needs to be applied to oils and change intervals
1 - read the Drivers Handbook and interpret what is needed for the way YOU operate YOUR vehicle
The engine designers knew/know best
2 - change intervals will become apparent to a normal sensible person - see 1) above
3 - never believe that changing premium oils more frequently than needed will prolong engine durability - getting the oil to operating temperature 90C+ often will have a better effect
Those persons using an SL/A3 oil or a fully synthetic oil that change their oil more than twice per year ( minimum use or very cold winters/very hot summers ) or about 15000 kms are simply wasting money. Use oil anaysis to prove this point if you wish
In my MY89 S4 I use a fully synthetic 15w-50 SJ/CF oil and change it every 15000 kms - I live in a very hot all-year-round climate
Oil consumption is virtually zero in this time
Finally I have been using synthetic lubricants in motor vehicles since the early 1960s. All of my vehicles cars, utes, trucks, are on synthetic lubricants - engines, diffs and gearboxes. Not a single brand. The diffs and gearboxes, once on synthetics are never changed again for the operational life of the vehicle - 200000kms cars - 1.5 million kms trucks.
I am an Automotive Engineer trained in NZ and England and 63 years of age. Experience does count!!
Regards
Doug

Bernie

I know,

That one cracked me up for about 10 minutes as well.

<img src="http://www.stopstart.freeserve.co.uk/smilie/jump3.gif" alt=" - " />

Great To Have You Here Jim......

Cheers
Bernie

Jim bailey - 928 International

Cummings article.... Yes that was very informative an article about engines in boats especially .." The burning of diesel fuel creates large quantities of water and various sulfur compounds. If allowed to remain in the oil..." So in this " experts" opinion ; water in the oil (and sulfur) is a result of burning fuel and not from humidity in the air which considering most yachts live in the water would certainly be humid . Article also states .." change the oil and filter at recommended intervals.." I note that he did not recommend changing it FIVE times as often . Oil analysis is very useful , Mark Anderson has been doing this for many years with his race car and as long as it is analyzed by the company selling the oil I would think they should have a good understanding of what their oil is made of when new and be able to determine the level of contamination , trace metals etc. I knew from the outset that trying to persuade anyone that 3,000 mile oil changes were excessive was unlikely . This discussion has now reached a point perhaps best described where "facts" , expert opinions are being used the way a drunken man uses a lamp post .....more for support than illumination . So naturally I omitted his reference to " the oil temperature has to quickly exceed the boiling point of water " . Which is interesting as it implies oil temperatures commonly exceed 212 degrees , in fact are designed to . The fact that Porsche used an engine oil cooler in the radiator implies that the coolant temperature is lower than the oil temperature and minimum recommended coolant temperature is about 185 F ; in fact the auxiliary cooling fan 1978 to 1986 does not even engage until the coolant in the tank where the engine oil cooler lives hits 198 F . So what did we learn from this discussion ? Water vapors in the crankcase are a by product of cumbustion and blowby . Oil temeratures often exceed 212 . Oil can last a long time . And thus far no " Lampost " supports the premise that engine oil needs to be changed FIVE times more often than the scheduled service . But go ahead tie a rope to the pig " better safe than sorry ". NOTE minimum oil change once per year reguardless of miles .

Jim bailey - 928 International

After reading Doug Hillary's post let me be the first to say . I know nothing about oil ......have known a few pigs but that is another story. Thank you Doug for taking your time to comment . I have to go find some more rope .....

Doug Hillary

Hi again,
Thank you Jim - I agree totally - I suspect the oil temperature in a Shark in this climate is up to or close to 120C at times. I have seen this in my wife's Golf ( oil cooled by coolant)

Engine oil in my trucks's have the following average coolant temp/oil temp relationship - Coolant 87C and oil 103C. Or oil about 20% higher than the coolant, on average. The oil cooler is in the coolant system of course
The Detroit's engine management parameter for oil is:
Shut down at 121C
Audible/Lights Warning at 115C
Normal up to 110C

I suspect the 928 S4 on a hot 42C day with a following wind would indeed have a fairly high oil temperature - but I have never measured it
I suspect though that the oil to coolant temperature ratio of about 20% higher would be applicable

My 1974 MGB with an oil cooler that was NOT temperature controlled but was in the oil gallery circuit, ran VERY VERY cold oil on a cold day. No where near coolant temperature. No wonder these BMC engines suffered from cold sludging!

As a matter of interest we could go beyond 100000kms oil drains in the trucks as the oil is still suitable - it is a cost/benefit decision of mine that we don't. Not that oil is non-servicable!

Jim, thanks for your obvious professional knowledge and your common sense

Bye now from raining tropical Northern Australian where we have rain today for the first time in about a year - and 27C

Doug Hillary

Fastest928

I still have not seen any light yet...

Here are some FACTS:
1 Navastar 7.3 diesel recommended oil change interval - "normal duty 6000 miles or 6 months, sever duty 3000 miles"

2 Saburu recomended oil changes:1st oil change
at 3 months or 3,000 miles with oil and filter change a minimum of every 7,500 miles.
For most stop-and-go urban driving, dusty, snowy or extremely cold or hot driving (maybe to subaru this is sever duty?) to change the oil and filter every 3,700 or 3 months.

3 Ford Motor Company recommends a 200 hour oil change interval for vehicles that are idled for long periods of time. In the example of a vehicle idling 24 hours a day and driving 50 miles, this would decrease the time between oil changes from 100 days to 8.3 days when compared to the 5,000 mile interval method.

Obviously, some of you folks know more about engines, use conditions, driving habits, internal conditions, oil types, etc. of individual engines then most manfuacturers of a piston engine vehicle! Doug, you know your engine quite well...good for you, your engines and your company! However, no 928 owner that I know has their engine oil tested regularly! I did not hear you say you test your 928 engine oil?

Most manufacturer have a "use" clause, obviously, you folks completely disregard this FACT cause you know better.

Help us out here.....are you saying that an engine "use" does not affect oil change intervals, condition of oil, etc?

Are you saying it is better to abuse the hell out of an engine, not be aware of that abuse and change the oil once a year cause there is "folklore" around more frequent engine oil change intervals? Yea, "abuse" takes many forms, one is just driving the little ole 928 around town in 1 mile increments....

Are you saying that it is better to be sorry than safe?

Marc
DEVEK

Drewster67

Honest questions here.

Does the amount of oil in the crankcase have any bearing?. In other words - does more oil mean less change intervals?.

T_MaX

Doug, here is my rebutal and the last that I have to say on this subject (GTS oil consumption).

1. If you turn your 928 @ only 2100 RPM's, your not driving it very hard and the motor and gear box should last you at least two life times (maybe) and changing your gear box oil once or twice every few years may work for you, hey it's your car. I have been in contact with many 928 owners over time who state that their rev limiters get bumped on a regular basis, so I guess they don't fit within your study group.

2. Prior to the mid 90's the piston to cylinder wall clearances for mid to large diesel engines were large enough that alowed small amounts of diesel fuel to pass the rings in curtain conditions (heavy use). This was an acceptable amout due to the lubicating properties of the fuel and oil change intervals (little cylinder wash). Hey! You forgot to mention the valves stems and valve seats and why has oil consumption of the big diesel motors not be mentioned?

3. I was under the impression we we talking about HD small, to large displacment diesel motors (i.e. Catapilar 3116 (S6), D398 (V12) , my mistake. Yes your right, the late model small displacement diesel motors that are in the light to mid size pick-up trucks put out buy Ford, Dodge, Chevy don't have clean-out panels. Kenworth, Peterbuilt, white, Autocar, Mack, Western Star and the like may or may not depending on MY and what motor was ordered when it was built. I have seen some of these with have removable inspection/clean-outs panels incorp. into the oil pans!

5. Again, Yes your right, the late model small displacement motors that are in the light to mid size trucks put out by Ford (*with what ever they can buy the cheepest and still compete), Dodge (*with it's old but reliable CUMMINS motor) and Chevy (Duramax with it's weak injection system), do not use ease replaceable liners. But as far as I know most if not all of the small to large farm impliment diesel powered equipment (US built) and HD mid-size and large diesel engines that see over the road use and industrial engines do have replaceable liners (no machine shop work required).

Doug, don't get me wrong! I think that changing any oil before 3-5K in a 928 is a waste of any type of oil and puts an un-wanted burden on our Eco-system, unless the engine in question is being run to it's extreem limits over 50% of the time (racing). As for Synthetic oils, well to each his own, I personaly perfer Red Line, Royal Purple and Amsoil over many of the mass hyped oil products out there and IMHO can be left in a bit longer (maybe the full 12K under normal driving conditions). I would still at the least change the filter at 6K if I were to run my oil into the 12K range (JMHO).

Do the new Cat. and Detroit motors not burn oil like it's being givien away? I know of many Shrip boats and oil rigs that use as much as 5 galllons of oil per 12 hour period (during heavy use). In these cases the oil never get a chance to get dirty

Ones like this used to have the inspection/clean-outs panels incorp. into the oil pans (may still) (small-size)
<img src="http://www.caterpillar.com/industry_solutions/shared/truck_engines/images/3306c.jpg" alt=" - " />

This one has/had removeable side pannels (mid-size).
<img src="http://www.caterpillar.com/products/shared/oil_n_gas/drilling/images/drill3.jpg" alt=" - " />

The oil sump on this one is so big, part of it is used as a walking platform (large size).
<img src="http://www.caterpillar.com/products/shared/oil_n_gas/crude_pumping^production/images/prodeng.jpg" alt=" - " />