molarman

This is what my audi dealer uses..any ideas? also, do i need to oil change more than the 5000 mile intervals? I have a 2004.5 with 2300miles on it? 1.8t thanks

1/4 scale

according to the recent campaign ... yes

Audi Junkie

M1 0w-40 meets the VW long-life spec 503.01 & 502, Belgian Syntec just meets the basic turbo 502 spec. In short, you can run a 1.8t 5,000mi on 502 or 10,000mi on the 503.01 long-life oil. In a V6, you could push the 502 oils to 10k if really desired. I like 6 month intervals with whatever oil you think you need. Just BYO oil to the dealer at 5000 miles and every mile recommended change or 6 months. I admit, 5,000 oci is a pain in the ***, especially to meet warranty. I have been going 6 months up to 11,000 miles on my V6 with German Syntec 0w-30 in it. It has the same specs as Mobil 1 0w-40. When in doubt, a Mercedes 229.3-spec oil is the same as VW 503.01.




Thanks Molekule for interpreting these papers...


Now some very good scientific sources that I rely on are found in the Journal of Synthetic Lubricants and a number of texts, one of them being Synthetic and High-Perfromance Functional Fluids, edited by Ronald Shubkin [PAO and Friction Modfier chemist and tribologist (PhD) for Ethyl Corporation]. Another one is the CRC handbook text, Handbook of Lubrication and Tribbology, Vol. III, edited by E. Richard Booser, Chemist and Tribologist (PhD) of Pennsylvania State University.

[Now unless you are a chemist or formulator, I wouldn't recommend rushing out and purchasing these books; they cost upwards of $275 each].

I will quote some info and then attempt to put into laymens terms. In order to do so, I will simply say R1, R2, R3 for the respective references.

R1, R2: Hydrolytic Stability:
"The hydrolysis of the ester, that is to say, their cleavage into an alcohol and an acid, has been the subject of many discussions in the past. However, this reaction has proved less disadvantageous in practice than had originally been feared. Ester lubricants must be hydrolytically stable because they are exposed to humid atmospheres during use and and come into contact with appreciable quantitites of mouisture in many applications. The hydrolytic stability of esters depend on two main features: processing and molecular geometry.
Acid value
degree of esterification,
catalyst used during esterification.

"Esters have to have a low acid value, a very high degree of esterification, and low ash level before the effects of molecular geometry will begin to assert themselves.
Molecular geometry can affect hydrolytic stability in several ways....."

"The hydrolytic stability of neopolyols can generally be regarded as good, and superior to that of dibasic esters."

Translation: Hydrolitic stability is not a problem today, and esters are today designed to be stable in the presence of moisture and acids, by their molecular engineering.

R1, R2: Elastomer Compatibility:

"Elastomers [synthetic rubbers as in seals] that are brought into contact with liquid lubricants will undergo an interaction with the liquid that is diffusing through the polymer network. There are two possible kinds of interaction: chemical interaction and physical interaction... Chemical interactions of elestomers with esters are rare."

Translation: The polymer network here is the polymer of the seal material. Interactions of seal materials with esters for lubricant oils are rare. That's why lubricants are tested for seal leakage in machines.

R1, R2: Polyols (Polyolesters): (general Information)

"Polyols are made by reacting multifuntional alcohols with a monofunctional acid....They are, however, much more stable than diesters, and tend to be used instead of diesters where temperature stability is important. A general rule of thumb is that a polyol is thoguht to be 40-50 C more thermally stable than a diester of the same viscosity. Esters give much more lower coefficients of friction values than those of both PAO and mineral oil. In general, polyol esters based on TMP or or PE give lower values [of friction] than diesters."

For those just tuning in, there are three major polyol esters: pentaerythritol esters, di-pentaerythritol esters, Tri, Qantinary-pentaerythritol esters, Trimethyl Propane esters (TMP), and Neopentylglycol esters (NPE). A fairly new one is the TME ester discussed earlier. All are very hydrolitically, thermally, and elastomerically stable.


On the topic of metal loss by various fluids:

From Lubrication Engineering, Volume 35, Table 4, Bench oxidation tests for steel, aluminum, copper, and lead catalyst, 163 C, 10 hours;

A 4 cSt mineral oil by itself shows a lead loss of 201 milligrams,
a 4 cSt PAO by itself shows a lead loss of 561 mg,
a 5 cSt alkylated aromatic (AN) shows a lead loss of 558 mg,
a 5.1 cSt dibasic ester shows alead loss of 11 mg,
and a 4 cSt polyol ester shows a lead loss of 40 mg.

So this oxidation test contradicts the one shown by Primus.

In the same paragraph of R4, "Proper additive selection is necessary to obtain acceptable engine oils from both mineral oils and synthetic base stocks."

In other words, whatever base oil you use, proper additive selection must be "tuned" to the type of base stock or mix of base stocks you are using.

Dichtomatic O-Ring Handbook
Section 5 - Compatibility, starts p. 141

At page 154 it lists di-ester synthetic lubricants compatibility with:

Nitrile or Buna-N rubber - Vol. change 10-20%
Fluorocarbon Elastomer - Vol. change <10%
Ethylene-Propylene-Diene Rubber - not suitable
Silicone Rubber - not suitable

Book doesn't list results of other rubbers tested with di-esters. I must carefully assume that polyol ester will have simular effect on rubber compounds.

pinoy@audi

lease? let the dealer take care of it. to own? every 5K.

Levent

That's what I use. Are you a dentist ?

molarman

yes. I am.

Levent

Me too :-)

1/4 scale

ugh ... this is painful! ... sorry guys couldn't resist ;-p

Audi Junkie

Audi is the quintessential dentists' car.

Levent

No problem. We're the bad guys ! ;-)