So what really causes sludge?

[A4NCAR]

- Ecessive carbon build up from non-synthetic oil?
- Is it caused by heat?
- Oil screen?
- Turbo?

Sludge issues have been a big topic with VW/Audi [AoA] recently and there are many rumors/opinions as to why exactly. IMO, it only seems to be a big issue here in NA because of the 3.7 qt oil capacity in the Audi A4 1.8t, using a cheap US dino crude, or synth, for 10K miles, as well as owner abuse from driving with low oil (I can't begin to comment on how many posts there are with; "Help, my engine oil warning light came on...", or "...there's no oil in my engine (dipstick), what do I do/use... will it hurt my engine... is it damaged.... should I change it...".

It'll be obvious to most here with some oil experience, that the 10K miles with a US dino crude is the first major error. But is this the only reason for sludge?
Anyways, AoA has addressed the issue with a letter stating the problem is known to them and that 1.8t owners must use an approved synthetic oil ONLY. They also began using a larger oil filter (increases oil capacity by .5qt), and now recommend/use it for '97-2004> 1.8t models. They also extended warranty for any sludge related issues, provided you use an approved oil with VW502.00 from their list. IMO, they only stated the VW502.00 and not the VW503.01 because it's the most widely available from the selection at local auotparts stores (Kragen, NAPA, WalMart,..gas stations,.etc.), and they want people to be able to find it easily. Although, if owners followed the recommended service schedule, then the dealer would have/use the proper oil at the 10K OCI service. But we know how many people are insistent on doing it every 5K miles, so they may take it to Jiffy Lube (who isn't going to pay any attention to oil approvals/quality), some other service station, or do it themselves. I guess changing the dino crude every 5K miles would be adequate though and shouldn't cause any sludge issues (w/ larger filter). But for me, I'd still use a 100%synth.

Thanks for your oil wisdom.

[ October 21, 2004, 03:27 PM: Message edited by: A4NCAR ]

 

[glxpassat]

I'm no expert, but it's my understanding that it's the shearing of the viscosity improvers that create sludge. In this situation 3 big mistakes were made - 1) using dino with a turbo that gets really hot, 2) small oil sump, and 3) 10k OCI. I mean, what were they thinking? Did they fire all of the engineers? I'm amazed that a company like VW would allow this to happen...

 

[MolaKule]

If you want the chemical-chain-reaction explantion do a search on 'sludge' or 'sludge precursors'.

 

[1 FMF]

I'm no expert either, but read the following link, specifically between figures 6 & 7.
My understanding is "sludge" is caused from cold oil temps and nitration, nitration being the formation of nitrates in the oil from combustion gasses. On the other hand, you have oxidation happening when the oil is to hot and vaporizing leaving varnish behind.
In both cases, insoluables are left behind... which can then be called [incorrectly?] sludge?
First determine what actually happened to the oil, then find out what operating oil temps and coolant temps are. With a turbo, what's the chance of increased blowby and combustion gases finding there way into the oil? What about from high boost pressures when the motor is cold? And for all the vehicles having problems, what climate are they operating in? If all are in moderate to cold climate regions, I'd look more at of a nitration problem. If they're all in hot climate areas, then maybe more of an oxidation problem. How about length of time the motor operates per a given warmup cycle? With my 2002 LS1, with a 195F thermostat my oil temp gauge shows oil only reaching 180F by the time I get to work in the morning, after a 14 mile and 25 minute city/hwy drive. Outside temp has been 50-70F lately. Back in the summer I had no trouble running 190-220F oil temps, even on a 160F stat. I guess aluminum (it's an all Alum. motor) really likes to shed heat, more so in the colder weather now. According to the link, nitration occurs at 175F and increases with oil temps of 160F and lower.

Like said in previous post, a very long oil change interval coupled with a small sump capacity plus the engine consuming oil to where the motor is operating on very little oil is only going to exacerbate the problem, in either case.
http://www.machinerylubrication.com/article_detail.asp?articleid=663&relatedbookgroup=Lubrication2

[ October 21, 2004, 04:16 PM: Message edited by: 1 FMF ]

 

[moribundman]

quote:

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IMO, they only stated the VW502.00 and not the VW503.01 because it's the most widely available

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The VW 503.01 oil spec is NOT BETTER than VW 502.00.

The difference is that that VW 502.00 oil is not suitable for LongLife service like VW 503.01. Vehicles that are equipped for LL service have a flexible service interval display. I suppose a VW 503.02 oil will thicken less than a VW 502.00 oil with an oil change interval of 20k miles or whatever the interval may be. The turbo TT, turbo S3, and turbo RS4 use VW 503.01 oil. All those cars can also use VW 502.00 oil, if regular oil change intervals are maintained.

 

[Asteroid]

Go to www.autosafety.org/ Action Alerts VW Oil Sludge Problems.

 

[Audi Junkie]

VW 502 = 5k intervals
VW 503.01=10k intervals

I've read the articles on sludge formation before. Interesting, but I cannot recite the chemical process verbatium. My impression was that impurities left behind during refining was the starting point for sludge and that's why Gruppe II, II+ and III do increasingly better in this regard. Slack-wax being the purest Gruppe III due to the fact it does not see the hydroprocess/hydrocrack treatment at all.

 

[ekpolk]

quote:

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Originally posted by Audi Junkie:
VW 502 = 5k intervals
VW 503.01=10k intervals

I've read the articles on sludge formation before. Interesting, but I cannot recite the chemical process verbatium. My impression was that impurities left behind during refining was the starting point for sludge and that's why Gruppe II, II+ and III do increasingly better in this regard. Slack-wax being the purest Gruppe III due to the fact it does not see the hydroprocess/hydrocrack treatment at all.

---

Interesting. Is there some other factor besides mileage that distinguished the two VW standards? I just checked the back of one of my many (

) GC bottles, and it indicates that GC meets both the 502.00 and 503.01 specs (and 505.00 is listed too).

 

[Dr. T]

I think the ultimate breakdown of the oil and it's constituents is what causes sludge. Number one culprit in my book would be heat.

That said, there should be a ranking amongst oils. Thin dino's would be on the top of the list. Hence the 3k OCI 'severe' recommendation not being off the wall completely when using these cheapo lubes.

Then you have the 10k OCI's in the UOA section

 

[labman]

Maybe it was growing up in Pennsylvania, but I always thought sludge came from polymerization of the nasty unsaturated material in the asphaltic Texan crudes.

There are 2 forms of polymerization, addition using unsaturated materials, and condensation using acids and polyols. There are 2 things that will never go in my crankcase, unsaturated vegetable oils, and esters unless known not to be mixtures of dibasic acids and polyols. You can make a great lube out of either form of ester, but mixing them is asking for trouble.

Broken down VII's are another problem.

 

[haley10]

Labman, does this make a strong case against not mixing any synthetics?? GC seems to be a mystery, so we don't know the composition. This could be scary, since a drain is never 100%.

 

[labman]

Just ones of unknown composition. If you are using a tri methylol propane or pentaeythrol based ester, make sure you don't mix in any phthalate or trimelitate esters. In the paint industry, we called the reaction products of such mixtures alkyd resins. Spell check isn't going to straighten out this post.

I lean in the direction that with all the oils on the market, surely I can find one that is close enough as is.

 

[farfel]

Can using diesel oil help absorb & carry away sludge?

 

[moribundman]

Audi Junkie wrote

quote:

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VW 502 = 5k intervals
VW 503.01=10k intervals

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Those figures don't match my experience. Even my 1989 Scirocco, which was still using VW 500.00 (replaced by VW 502.00) had an OCI of 15k km (ca 9.5k mi). The OCI for my '96 Audi, which is supposed to run on VW 502.00 oil is also 15k km.

ekpolk wrote

quote:

---

Interesting. Is there some other factor besides mileage that distinguished the two VW standards? I just checked the back of one of my many ( [Roll Eyes] ) GC bottles, and it indicates that GC meets both the 502.00 and 503.01 specs (and 505.00 is listed too).

---

Seal compatibility may be different, but if an oil meets both specs it's not an issue. VW 505.00 is for regular diesel engines (not Pumpe-Düse) without LongLife service.

 

[Audi Junkie]

Mori, your car was not a turbo.

 

[moribundman]

Audi Junkie, are you saying VW/Audi requires 5k mile oil change intervals in turbo engines that run on VW 502.00oil and 10k mile intervals in engines that run on VW 503.01 oil? What exactly is the OCI according to the 1.8T manual?

 

[Ken2]

One part of the VW problem is that dealerships (like my local one) were using bulk 5w30 instead of a better quality oil.

My understanding is that the main cause of sludge is oxidation of the oil which is accelerated by heat. Contamination of the oil by coolant or other outside products also causes a sludge, but that's not the usual cause.

Interesting article in "Lubes & Greases" this month. They're talking to European car makers about the recommended oils and maintenance intervals. The tendency there is to use much better quality oil. To summarize, A3 quality oil is about good for 10,000 miles or 1 year. Long-life oil spec'd by the car maker is good for maybe 20,000 miles or two year service intervals. Some passenger car diesels with their long-life oil are good for 30,000 miles. The feeling there is that the car owner's time during maintenance has value, so the high priced oil is not a problem. They have little use for oil of such low quality as API-SL, etc.


Ken

 

[Steve S]

A simple explaination of what causes sludge, Not changing oil soon enough.

 

[ekpolk]

quote:

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Originally posted by Steve S:
A simple explaination of what causes sludge, Not changing oil soon enough.

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Alas, in this case, simplicity is an illusion. Unless we know how soon is soon enough, the answer is not useful. Too long and your engine fills with varnish and sludge. Too short and you just waste money on unneeded oil changes.

 

[Audi Junkie]

Mori, I reread your post. I was saying exactly that which you quoted, but it is not from any one manual. 503.01 simply appeared at the same time as dealer 10k intervals, 2001. Prior 1.8ts had 5k intervals from 1997 onward. BMW LL-01 is the USA 15k spec, it's from '01! MB 229.3 seems to be in there at the same time, I dunno exactly. VW 502 and A3 are earlier specs (1998?) and I believe MB and BMW have corresponding A3-based specs.