which is the best oil

  #1  
Old 09-10-2005, 03:47 AM
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Default which is the best oil

Hi everyone, I just bought my first Audi. It's a 92' A100 2.8 with Quattro. I already ordered a repair manual but it won't be in for a few days. I wanted to change the oil right away (or else I'd wait and see what the book recommends) so I figured I would ask the experts which would be the best weight and viscosity of oil to use. Thanks alot!
-Matt
 
  #2  
Old 09-10-2005, 12:04 PM
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Default RE: which is the best oil

Its dependes of you, on geographic placement.
If cold place go with lower 'w' number, else higher 'w'
and if you don't know which oil you have then use syntetic blend, for couple of times then switch into which you like.
if you switch directly mining jump from syn to organic then you will have problems of bad oil, it will go bad after first 1k miles or less. but if you use syn blend then you will be doing regular changes like 5k miles I think.
DO not jump from syn to org or org to syn directly do : (org)-blend-blend-syn or (syn)-blend-blend-org
to get best try to keep the end number high but the 'w' number change for example for summer use 15w-50 or 10w-40 for winter 10w-30 or 5w-40 for even colder winter 0w-20
I live in brooklyn, ny and usually use 10w-40 syn for winter 10w-30 or 5w-40 syn
PS: 'w' is not 'weight' its 'winter' two different thinks the second number represents the top temperature. basically ??w-?? gives you temp range
 
  #3  
Old 09-10-2005, 07:01 PM
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Default RE: which is the best oil

Oil weight, or viscosity, refers to how thick or thin the oil is. The temperature requirements set for oil by the Society of Automotive Engineers (SAE) is 0 degrees F (low) and 210 degrees F (high).

Oils meeting the SAE's low temperature requirements have a "W" after the viscosity rating (example: 10W), and oils that meet the high ratings have no letter (example SAE 30). An oil is rated for viscosity by heating it to a specified temperature, and then allowing it to flow out of a specifically sized hole. Its viscosity rating is determined by the length of time it takes to flow out of the hole. If it flows quickly, it gets a low rating. If it flows slowly, it gets a high rating.

Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil. You will hear them referred to as multi-viscosity, all-season and all-weather oils. An example is a 10W-30 which is commonly found in stores. When choosing oil, always follow the manufacturer's recommendation.
if you switch directly mining jump from syn to organic then you will have problems of bad oil
- BS, manufacturers like to make you to believe that is the case. So once you switch to the more expensive stuff you will continue to give them money.

W- doesn't stand for winter but weight. You can buy a straight 10W or 30W oil.

By Federal law all motor oils are supposed to be compatible, mixable and interchangeable. I have switched back and forth many times and my engine at 176K has not blown up! I will use light synthatic oil during winter 5W-30 and regular 10W-30 during summer. If you go with 10W30 year round it is not a problem. 10W30 indicates multi weight and represents viscosity. A 10W30 oil is an oil that flows like a 10 weight oil but lubricates like a 30 weight.

What ever oil you chose to use make sure you change it on a regular basis like 3K miles and don't use Fram filters, they are of the worst construction. Purolator, AC Delco, have gotten high marks from independednt test labs. I like using Pure One from purolator but use with caution this filter cleans too well and if you go well beyond 3K it will clog up.
 
  #4  
Old 09-10-2005, 10:05 PM
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Default RE: which is the best oil

Thanks for the help guys. I'm sure this won't be the last time I call on Audi Forums for advice!
 
  #5  
Old 09-11-2005, 01:14 PM
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Default RE: which is the best oil

wrong. 10w-30 means
it will flow like 10 in 0 C and 30 in 100C it has nothing to do with lubrication not direct any way.
there is a addictive that they add to make so it doesn't lubricate called VII, well why wont you just read it
An oil sold as 10w-40 is no thicker than 10 weight oil under Winter (10w) conditions, meaning below freezing. The 40 means it is no thinner than 40 weight oil at 212° Fahrenheit. So, the first number tells us the performance of the oil at or below the temperature of freezing water, and the second number tells us the performance at the temperature of boiling water. The chemicals added to the oil to accomplish this are called Viscosity Index Improvers (VIIs).

To make a 10w-40 oil, the manufacturer would start out with a 10 weight oil as the base stock. All by itself, this oil would thin out so much at normal operating temperatures that the oil film would be useless. So, they add these very special very long molecules, the VIIs. The VII molecules are as much as 1000 times as long as an oil molecule. The VII molecules curl up in a little ball at room temperature, but as the temperature gets higher they uncurl and stretch out, like a cat sleeping in the sunlight. The more stretched out the molecule is, the more it impedes the normal flow of the oil, thus raising the effective viscosity. Now, this sounds just a little too good to be true. Well, there are two catches: first, these molecules are not lubricants, so the more of them that you add the less oil you have sitting around lubricating things. Secondly, these VII molecules can be broken into pieces by various pressures and forces, like being squeezed through the transmission gears in a motorcycle or the hydraulic valves in a diesel engine. Every time a VII molecule gets broken, the oil loses some of its high temperature viscosity. Synthetic oils made from pure PAOs and/or Diesters typically have very few VIIs, so these oils are far less subject to viscosity breakdown due to shearing of the VII package. As a result, synthetics are far more stable in a motorcycle engine.

10w-30 oil increases its viscosity at high temperatures by a factor of three, which requires a significant amount of these VII molecules. 10w-40 oil increases its high temperature viscosity by a factor of four, which requires even more even longer molecules. 20w-50, which sounds a lot like 10w-40, only increases its high temperature viscosity by a factor of two and a half, so it requires fewer of these molecules than even 10w-30. 15w-40 also increases its high temperature viscosity by about two and a half, so this oil is also substantially more stable than 10w-40. Most passenger car oils today use inexpensive VII molecules that break apart relatively easily. Conversely, most diesel engine oil VIIs are chosen from more expensive chemicals that are more shear stable, since an oil change in a large diesel is expected to last for 15,000 to 150,000 miles.
I usually use S/C oil that works both on diesel and gassoline engine, the reason is that diesel oil is better cleaner and have a bit better proparties. if you have a lot of burned oil in your engine then use S/C class oil to clean it up. I have mazda626 and idiots in my garage put in regular oil, it went bad in 1000 miles, so I had to switch into syn-blend each about 2.5k-3.5k for couple times then switched in for Mobil1 extended performance and now I have about 5K on it and still running.
for my audi I will use syn blend this time 5w-20 or 10w-30 for winter.
The reson why you should NOT blend organic and syn oil that they use simmilar but different addictives, and addictieves in organic oil will attack the syn oil and destroy it faster and it works opposite too. Its like when doc puts B blood into A person, DEAD. The Syn blend can work both syn or organic, and can be easilly changed into anything.
BUT there is some exeptions, some addictives will be fine with foreighn oil, so you can switch between organic and syn oil right away, but you don't know which is which so I wouldn't take chanches.
 
  #6  
Old 09-11-2005, 02:49 PM
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Default RE: which is the best oil

  #7  
Old 09-11-2005, 04:12 PM
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Default RE: which is the best oil

No offense kakarot but I am having trouble reading your post. I enjoy reading it, as it pertains to me as well, but can you be a little more articulate? Sounds like ebonics...
It's difficult transitioning from point/counter-point when it sounds like two different languages.
 
  #8  
Old 09-12-2005, 12:05 PM
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Default RE: which is the best oil

The link is interesting but obviously an opinion of one individual that I have never heard off in the automotive world.

I have mazda626 and idiots in my garage put in regular oil, it went bad in 1000 miles,
I am curious to know what you mean by "bad"? Did the engine seize? Did you have to rebuild it as a result?

Here is what I have learned over the 20+ years I have been reading and working on various automobiles.

I have an automotive machinist who has been building +600HP big-block stock cars for 40+ years. He also races them and has plenty of loyal customers who race his engines and win. He told me that he buys what ever is on sale. His conclusion is that most oils are the same when it comes to daily drivers, as long as you change the oil at no more than 3000 miles. He also uses regular oil on his 650HP non-blown stock 68 Camaro and gets some impressive ¼ mile numbers at the strip.

Today’s oils have plenty of additives and the difference between various brands and types is the proportion of these additives that are added. The additives consist of various viscosity altering qualities as you mentioned. An acidic additive is used as detergent to clean the carbon and burned oil deposits. Then there are various additives added for anti-coking, zinc for metal to metal protection, emulsifiers, anticoagulants, blah, blah.

The old SAE10 had no additives and you can still buy it with some difficulty. It is still used on a lot of old farm equipment and machinery. The straight non additive oils will look the same after 5K miles, but the engine will have black burned oil scale on all internal parts. Over time it will restrict oil passages resulting in oil starvation and failure. It is these additives that turn the modern oils black and eventually to sludge as the oil is designed to hold these particles dissolved in suspension until the oil is changed. The interesting note is that the detergent and additives are the ones that break down and not the oil and it happens rather quickly, I heard within the first 1K. So if you want to scrub your engine clean, change the oil every 1K for the first 5K miles.

If you are going to store a vehicle for a long time you will be better of using straight SAE oil because it contains no acid that will etch away at the main engine bearings. I have a metal lathe and the manufacturer recommends straight non additive SAE20 oil because motor oils contain acid which will etch away metal and reduce accuracy.

I put about 20-30K per year and just about all my cars are high mileage. I change the oil and filter at about 3K to 4K intervals regardless weather it is synthetic or regular oil. When I pull the oil pan or valve cover off I have no sludge or scale in my engines. The oil pressure is well within the factory spec and on startup I have no noise coming from the bottom or top end.

The is another good reason for frequent oil changes, most modern cars have way too small oil filters. The cleaning power of these puny things is joke!

To sum it all up: the synthetic oil do last longer but the detergents do not. I like synthetic during winter as it flows a lot better and faster then regular oil of the same rating. If you use correct recommended oils and change it frequently (3K) the engine will last a long time. I have seen what a synthetic oil looks like after 10K miles or even 6K no way I am going to subject my cars to such abuse.

Just my 2¢!
 
  #9  
Old 09-12-2005, 08:02 PM
Join Date: Aug 2005
Location: Brooklyn, NY
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Default RE: which is the best oil

I bought the car, the mazda626. Drove it for 1000 miles and decided to change the oil. So I went to my mech and used his oil. I think it was castrol 10w-40. Drove the car and about aftrer 700 miles, the light for oil started to hold on longer about 2 sec after the start. Looked at the oil and It was black as black hole. took off the cap for oil refil, also a lot of black sludge inside. had to do cleaning to get rid of some of it.
PS when I inspected the engine at the dealer, before I bought her, It was all clear without any sludge.
now I use syn oil and it doesn't start to get black for 2000 miles.
 
  #10  
Old 09-12-2005, 11:24 PM
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Location: Swamplands of NJ
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Default RE: which is the best oil

I think you got short changed by your mechanic and prematurely blamed the oil! Either he didn't change the oil at all and or he used a cheap filter. I have seen this twice, check the dipstick before you leave. Off course there is no way of knowing if they put in new oil or recycled. I got shafted and short changed way too many times and as result started to do all the work myself. It's bad enough that they can't get the job done right but it really burns me when they totally f**k it up and then deny it.
 

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