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  #16  
Old 05-21-2003, 06:54 PM
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Wayne Scraba, Valvoline website explained it a little,

high-viscosity oils maintain a higher oil pressure, but the pump delivers a smaller volume of oil.

lighter-weight fluid is easier to pump and therefore circulates faster through the engine's various galleries

The difference between a multigrade and a singlegrade oil: The singlegrade can't pass the low temperature viscosity test. If it did meet one of the "W" viscosities, it would be a multigrade.


"Oil Duties
Inside an engine, oil is in a Catch-22 scenario: It has to seal rings and valves, but it also must reduce friction. In simple terms, oil has to accomplish two functions that have directly opposite requirements.

The viscosity of any oil changes with temperature. The higher the temperature, the lower the viscosity—the oil thins out. On the flipside, the lower the temperature the higher the viscosity. Because of this, the Society of Automotive Engineers (SAE) has established a series of classifications that establish oil viscosity at 100 and 0 degrees Celsius (212 and 32 degrees Fahrenheit, respectively).

Highs and Lows
Low-viscosity oils flow better than high-viscosity ones—the lighter-weight fluid is easier to pump and therefore circulates faster through the engine's various galleries. Low-viscosity oils also maintain a lower oil pressure, but the oil pump delivers a greater volume through the galleries than it would with thicker (higher-viscosity) oils. Heavier oils also tend to operate at higher temperatures because the oil pump has to work harder to force the lubricant through the system. Oil does not compress readily, so the added pressure increases the temperature. In the end, high-viscosity oils maintain a higher oil pressure, but the pump delivers a smaller volume of oil.

Multigrades
Multigrade oils typically begin as base oils, such as 10W. Then viscosity-index modifiers (polymers) are added in an effort to stabilize the viscosity. This allows a SAE 10W-40 oil to flow like a 10W at cold temperatures and a 40W at higher temperatures.

The multigrade oils' viscosity modifiers are long-chain molecules that lessen the change of viscosity with temperature variance. In the past, the polymer additives (used to thicken the oil) were sometimes susceptible to viscosity loss. Permanent viscosity loss occurred when high shear forces (such as the relationship between the main bearings and the crankshaft) actually break the polymer molecules into less-effective smaller pieces. On a similar note, temporary viscosity loss also occurred when the polymer molecules aligned themselves in order to create a path of least resistance.

Multigrade or Multi-Vis?
One oil manufacturer claims that "some people in the industry use multi-viscosity as if it means the same thing as multigrade. An oil cannot be multi-viscosity, but it can be multigrade by meeting the viscosity requirements for SAE 30, 40, 50 or 60 and one of the sub-zero "W" viscosity requirements. At one time, some oil companies labeled oils SAE 10W, 20W30—as if the oil could be 10W and 20W at the same time. This is impossible because 10W is measured at -25 degrees C and 20W is measured at -15 degrees C, which eliminates the multi-viscosity theory.

Fortunately, today's additive packages have improved oil's shear-resistance. However, oils with the same rating from different manufacturers can exhibit different viscosity ratings in an operating engine, depending on the shear stability of their viscosity-modifying additives.

For technoids, weights are defined thusly (stokes and centistrokes are measurements of viscosity):

"SAE 30 is SAE 30 no matter what the "W" prefix number is: 0W, 5W or 10W. This viscosity in centistokes (cSt) @ 100 degrees C is with the minimum of 9.3 cSt and a maximum of 12.5 cSt.

"SAE 40 is SAE 40 no matter what the "W" prefix number is: 5W, 10W, 15W or 20W. The viscosity @ 100 degrees C is within the minim of 12.5 cSt and a maximum of 16.3 cSt.

"SAE 50 is SAE 50 no matter what the "W" prefix number is: 5W, 10W, 15W or 25W. The viscosity @ 100 degrees C is within the minimum of 16.3 cSt and a maximum of 21.9 cSt."

I am still debating using 10W30 or 10W40, although I am leaning towards 10W40 for summer.
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Last edited by zafarhayatkhan; 05-21-2003 at 07:10 PM.
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  #17  
Old 05-21-2003, 08:08 PM
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Well!

I don't know if I am any clearer on my orginal question .... other than 30 weight is too light for summer in N. California .... but this is very interesting discussion and we haven't touched on brands! (Nor do we need to!!! :-)

Thanks,

Haasman
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  #18  
Old 05-21-2003, 09:08 PM
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Thumbs up Temp doesnt appear until...

5 or 10 minutes into the running of the car. I havent used the block heater yet, as I discovered teh cord a week ago. I am quite wary of driving normally in my part of the country with a cold engine, as it is quite hilly here in the Ozarks.

I had one car that became quite pissy if I didnt give it at least 5 minutes to warm in a month that contained an 'R'.

Anyway, thanks for all the good advice {cough}Castrol GTX{cough}{cough}.

Quote:
Originally posted by haasman
moparmike

It is my understanding that "giving the engine 5-10 minutes to warm up" is not a good idea. You should let it run for 30 seconds max and then drive off. Once temperature appears on your temp gauge then drive normally.

An idling engine does not warm the same way as an engine that has some RPM and load does.

Haasman
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  #19  
Old 05-21-2003, 10:36 PM
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Most of the engine wear occurs at startup. Thicker the oil, the longer it takes for it to circulate.

In my opinion, if the ambient temperature routinely goes above 100F, 10W40 may not be a bad choice, but for temperatures going upto to only 80F, 10W30 or even 5W30 should work fine.

Before my Mercedes, I did not give the Oil grade much thought. Used 5W30 year round in Indiana, in all of my vechicle which ranged from 94 Passat, 2000 Maxima, 98 Montana, 87 300ZX, 89 Galant, 82 Century, Taurus, Probe etc.

I belive that with the MB, all of us on this fourm have an emotional attachment and we pay attention to a lot of small details, and MB's can be expensive to repair if something goes wrong!! and we keep them for a longer time.

As far as manufacturer's recomendation, I do not think it means much. All modern engines are fairly similar and operate under similar pressures and temperatures. I do not belive that auto makers collect historic data or do extensive testing, as everything keeps on changing, the oils, engines etc. are under constant development. They probably rely on oil manufactures's data.

All they can do is guess. A good example is the Mercedes FSS system and the associated engine problems relating to sludge etc. Computer models can give an idea, but the real world has too many variables. It becomes more of an ART then Science.

As an engine gets older, thicker oil can be useful at that time.

The best recomendation would be to choose engine oil based on ambient temperature and driving style.

Just think of the temperature in centigrades, so SAE 30 would be good upto 30 deg C, same thing with 40 and 50. The number before the W (which stands for winter) means that due to the addition of polymers, the oil behaves like a thinner oil at low temperatures.

As far as brands, all are similar. In Oils, Polymer additives are a little different. In fuels, fuel detergents are a little different, but the basic product is the same.

Automotive suppliers supply the same componets, eg. from Axles to piston rings to ignition systems with slight variations to OEM's. A lot of the componets are developed by the suppliers. Same thing with the oils. I am sure that all major brands have pretty much the same product.
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Last edited by zafarhayatkhan; 05-22-2003 at 04:36 PM.
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  #20  
Old 05-22-2003, 12:12 AM
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zafarhayatkhan,

I agree with the notion that it is more of an emotional decision to use the thicker oil in your engine.

Let's take a different vehicle altogether to use an example for a 'oil issue'. We will us my old vehicle - a 2000 Silverado truck w/ the 5.3L V-8. This motor - all 328 cubic inches of it is a clean sheet design from GM and forms the basis for the LS-1 design in the Vettes. Let it be noted that there is a class action lawsuit against GM for the 'piston slap' that is noticed by over 1/3 of the customers. The engine basicly 'Knocks a little' on start up. Let it also be known that in the owners manual for the '99 up Vortec truck line it is NOT recommended to EVER run 20w- 50 in those engines! They say stay with the 10w - 30 all the way up to death vally temps! I tried 50w mobil one in my truck just for kicks & it did not help!
My truck & also a friends truck started rattling upon start up at approx 10k miles. It is 'normal' to hear this on someones new body Tahoe, Silverado, Escalade sometimes. Let it be known that GM started spraying a polymer coating in the pistons in mid year '00 to 'quiet' them down for a while so customers wouldnt catch on to the sound. (for GM it just just buys 'em time for warranty work) The pistons are designed to expand when they heat up & that is why some think that thicker oil will provide the band aid/'cushion' for their engines. There has not been a rash of siezed up or damaged engines stemming from these power up knock noises. It is part of owning a chevy truck now & that is how it is!
check this site out - www.pistonslap.com

I'm not saying that GM engines are built tighter or MB's engines are built looser or BMW is better than MB or whatever. Like someone posted earlier, every car is different & there are to many variables to settle this opinionated debate on any fact?

A recent Car&Driver test of the new M3 says that they had to add 1 qt of oil at the 1,900 mile mark to show full. The press car is apparently clearenced looser for hp tests & burns more oil? Adding 20/50 wont fix that issue!

My MB owners manual for my C36 AMG says use 'use recommended oils' ........& thats it!

further checking in the manual says that "the dealer will have the proper info on what type of oil to use" Sounds like they want to get you at the stealership so a service writer can get you in to make some sales! My car came factory filled with Mobil One synthetic so that is what I have been putting in mine...10w/30 baby! I feel more comfortable knowing my main bearings are probably at least getting some oil at 5,900rpms & my oil pressure is not in the stratosphere.
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  #21  
Old 05-22-2003, 11:24 AM
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To address Haasman's original question, just use whatever weight the owner's manuals say to use. Both of my Benzes owner's manuals say that 10W-40 is the recommended "year-round" weight. The owner's manuals don't split between dino oil and synthetic they just list weights. I work with someone who has a 1985 Ford T-Bird Turbo Coupe 2.3l 4 cyl. He is the original owner and has always used 10W-40, per your request I won't mention the brand, every 3K. The car currently has 191,000 miles and has never been opened up. I agree with what another member said, that we can sometimes get carried away with the details about oil. The winning formula for oil is to change the oil often. The owner's manuals for pre FSS cars say to change the oil every 5k, under "normal" conditions. Mix in stop and go driving, towing, long periods of idling and short trips (real world "normal" driving), change the oil every 2500 miles. Simply because of that recommendation, I change the oil every 3K, since my driving and most peoples is a mix of the two.
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  #22  
Old 05-22-2003, 03:44 PM
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Hassman,

I researched this for you a little and as far as Mercedes Benz is concerned, they recommend everything from 0W to 50W for various temperature ranges. 10W30 and 10W40 is shown in the same temperature range with an arrow pointing up after 30C.

GM strongly recommends against using 10W-40 due to the excessive amounts of polymer additives.

I would recommend using 10W-30 in summer and 5W-30 in winter. Unless you drive under the following conditons:

Extended speeds in excess of 100 MPH, in temperatures above 100F and/or 150,000 miles on the odometer. You will have to increase the tire pressure by about 8 psi in high speed conditons as well.

Zafar
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  #23  
Old 05-22-2003, 03:54 PM
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Zafar

Thank you for you research.

I have to say that driving with 10W-30 in the summer just gives me a bad feeling (very unscientific!) It seems too thin.

The GM concern regarding rapid polymer deterioration in the 10W-40 oils is something I have heard repeatedly, even before seeing it here.

I am thinking of going either to a 20W50 or 15W-40 .....

Haasman
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  #24  
Old 05-22-2003, 06:05 PM
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I would like to point out two final obervations:

Engine wear at startup

Engine operating temperature staying roughly the same, regardless of the ambient temperature
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  #25  
Old 05-22-2003, 10:31 PM
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FWIW, add my vote to the "follow the manual" category--although there's still latitude there. My 560SL manual specifically confines 10W-30 to ambient temps under 50F. Preferred options for 32F up to over 86F, which covers my driving season here in Michigan, are 20W-40, 20W-50 or SAE30. What I've started running is 20W-50 formulated for high-mileage engines, which describes me at 146K. The 10W-30 that somehow got in there at the last change (NOT my idea!) definitely wasn't the ticket for stop-and-go traffic at 70F ambient; loading up with blue smoke from rest, not noted since the change. Guess it's another vote for RTFM.
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  #26  
Old 05-23-2003, 01:17 AM
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what an interesting discussion.

i think that i shall offer you another perspective.

until 7years ago, i never used a multi-grade oil.

my first benz was a 1973 220. was the original owner. ran it for 3 years and 140,000 hard, fast miles in texas. from christmas to easter i ran a valvoline 30 wt racing grade, for the rest of the year a valvoline 40 wt racing grade.

changed oil every 3,500 - 5,000 miles. never noticed any significant oil consumption for that 4-banger.

replaced it with a 1976 450sel. ran the same oils the same way. traded it at over 200,000 miles in 1985 for one of the first 300e's. engine never experienced any significant lube oil consumption. replaced the timing chain at 120,000 miles. no other engine work.

hated the 300e, traded it for a 1986 560sel. ran the same oils. no significant oil consumption. then my old mechanic expired and my new one was devoted to multi-grade oils. it was probably normal wear and tear, but within 20,000 miles on multi-grade stuff, this engine began to experience significant consumption. principally down the valve guides. so at 220,000 miles heads were pulled. what a nice looking engine in most aspects. cylinder 2 left exhibited some scuffing in the top ring reversal area but all the rest were virtually as new. camshaft lobes exhibited some wear. at this stage, engine was consuming 1 qt per 500 miles, and it went to this level fast: had been 1 qt per 3,000 miles and then instant consumption of oil. piston crowns were beautiful - perfectly clean.

cams replaced, valves replaced, guides replaced, timing chain replaced.

since this upper end renovation, engine is tight. no oil consumed between 3,500 - 5,000 change intervals with the multigrade. only complaint that i have is that the hydraulic lifters take too long to pump up in the morning at 30 sec-120sec idle.

that is my last benz that ever ran on a single wt lube. all my others have always been subjected to the multigrade philosophy. my 1987 560sec, i am the second owner, was always subjected to manhattan benz and multi-grade. had to renovate the top end at 65,000 miles. piston crowns were covered in gummy lube deposts. valve guides and valve stems in deep trouble. camshafts with more wear than my 560sel at 220,000 miles. po had oil changed every 3,000 miles according to the service records. my guess is that the engine was never run. after all, 42,000 miles in 13 years.

anyway, since top end renovation, engine is tight and no significant lube consumption over the last 15,000 miles. and no lifter clatter at start-up. but the oil pressure gage does drop to very low levels when the engine is warm and idling.
picks up into the normal range when the revs increase.

my 1995 e320 cab is so young, 10,000 miles, that it remains tight and quiet and leak-free after all this time on multi-grade oils.

all oils used are mineral.

my conclusion is that i am not sure that i can find any reasons against using a single wt oil for a hard driven benz in southeast, south central texas.

but i am all ears to other pov's.
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  #27  
Old 05-23-2003, 03:24 AM
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Albert,

Thanks for your input on this .... it is getting very interesting. Your experience with multi-grades is basically the same as mine. From the Porsche days I would either run 30 weight winter and 40 summer or run 20w-50. But in those days the only 20w-50 was for racing applications. No decent anti-corrosion additives and it always worried me in a street engine.

I think the real curve for oil considerations now are the synthetics. I think a 15w-40 synthetic may be the ideal way to go. I would probably stretch my change intervals from 5k to 7k since I do a lot of freeway driving.

Haasman
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  #28  
Old 05-23-2003, 12:40 PM
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CBDO,

Use the latest oil recommendation charts. These are updated periodically and manufacturer recommendations have changed over the years, as have the oil and the engines.
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  #29  
Old 05-23-2003, 05:15 PM
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Mercedes (and BMW) still specify thicker grades of oil than the competition. MB says 0w-40 and 15w-50 are fine and I prefer 15w-50.
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  #30  
Old 05-25-2003, 04:10 AM
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Just changed the oil in the 190e (215k miles) to 15w-50 synthetic.

Remarkable difference. Engine is much smoother. Both passengers noticed it immediately, at idle and while driving. Much quieter as well.

I believe there are two reasons .... first the benefits of a synthetic oil which is 50 weight, but also because the chain tensioner probably got pumped up or cleaned out and the engine timing being improved.

Haasman
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