What synthetic oil was this dealership using?
There are good non-synthetics and semi-synthetics available everywhere today, but I have to tell you, most oils today are composed of Group II-V base oils even when advertised as mineral oils.
Almost every lubricant used in plants today started off as just a base oil. The base oil category defines what the oil is made of, how it is manufactured, and how the lubricant handles certain environments such as extreme heat.The American Petroleum Institute (API) has categorized base oils into...
www.machinerylubrication.com
As
@BMWTurboDzl stated, there was an early learning curve for synthesized (PAO) oils. But it was not because they were too slick, but because they did not include the proper seal swell chemistry.
Earlier, Amsoil marketed a synthesized oil but it was of a different base oil, a Group V ester. They had no leaks associated with this formulation. Later, as many others did, they switched to a PAO plus other groups and additive mixes that provided seal swell.
Historically, it was Mobil and its early copyists, in my opinion, that screwed up when they used a majority PAO but with insufficient or no seal swell components. I.e., in an effort to arrive on the scene early, it was not fully tested with existing seal technology.
Since 1972, there has no longer been a seal swell/leaking problem.
quote:
Now I thought one of the good points of synthetics was that all the molecules were the same approximate size, whereas there is much variation in molecule size with a dino oil. It seems the mixing of two different weight base oils negates this presumed benefit.
Not quite. The advantages to synthetics (PAO's in this case) is that the PAO molecules have a narrow distribution of
different molecules of nearly the same size for a particular viscosity, whereas the mineral oils have a wide distribution of many different types of molecules of different sizes...
"...
Seal Swell (Performance Additive): nitriles, specific esters, organic phosphates and aromatic hydrocarbons. Increases volume of elastomeric
seals..."
Here is a comprehensive list (best you'll find outside of the lab) of multifunctional additives and their functions. Notice the same chemicals and compounds perform more than one function.
Multifunctional Additives (in Alphabetical Order) listed as to Functional Agent, additive category, general or specific chemical compound, and how it works, respectively.
Antifoamants or foam inhibitors (Protective Additive): polymers such as silicone polymers and organic copolymers of the silaxane's; creates a lens that reduces the bubble's surface tension.
Antioxidants or oxidation inhibitors...
Ok, this one may be a bit tougher.
Various organic Phosphates, Nitriles, aromatic hydrocarbons, and esters have been developed to affect:
1. what component in an engine or transmission, or hydraulic systems?
2. And how does it affect this component?
[ July 22, 2003, 01:29 PM: Message edited by: Patman ]
The answer is E and B in that order.
Seals can be damaged by mechanical abrasion, heat, and chemical attack. Sludge formation is the most prevalent form of seal degradation. But why sludge? Sludge contains high polarity and very small molecules such as amine molecules from various additives, most notably, the dispersants. (Microfine abrasion particles such as metals and silicon can damage them as well, but modern filtration usually removes most abrasion particles).
While esters can cause seal swelling by altering the plasticizer a bit, Dispersants not only can extract the...
Seal Swell:
For automotive engines and transmissions, the targeted seal swell is generally around 12%, whether the base oil is mineral, majority PAO, PAO/ester, partial-synthetics, or high ester content fluids.
A test by the ASTM, ASTM 6546, will provide a better set of testing rules for up to 1,000 hours of testing at actual service temperatures.
Contrast this for aerospace hydraulic systems, where milspec MIL-H-5606, allowed an acceptable range of 18-30% seal swell volume. The seals used are ACN NBR's, or high-acrylonitrile seals of butadiene-acrylonitrile elastomers.
The latest...
