quote:
Originally posted by G-Man II:
Just to clarify, hydrocracking and the synthesis process to produce PAO are both catalytic processes that utilize hydrogen, heat, and pressure. And both use molecular reshapping catalysts. So it's really an over simplification to state that Group III (or even Group II) base oil is just "highly refined" crude oil. In hydrocracking/isodewaxing, the larger molecules of the feedstock are cracked and reshaped into smaller molecules, and the residual wax is isomerized, to form a base oil. And the final step is further hydrofinishing. With PAO, the smaller molecules of the feedstock are "built up" and shaped to form a base oil. And the final step is further hydrofinishing.
As I pointed out in another thread, in the early days of gasoline production, when demand began to rise with the advent of cars powered by internal combustion, the oil companies had to develop a new way to produce gasoline since the amount produced naturally through distillation wasn't enough. What they came up with was "cracking" the larger crude molecules to produce gasoline. This "cracked" gas was commonly referred to at the time as "synthetic gasoline" and was universally lauded for its superior properties, including a much higher octane than "natural gasoline."
Hydrocracking involves the restructuring of the feedstock molecules to the point that they don't resemble their original state at all. It would seem, then, that the final product of hydrocraking can lay claim to being "synthetic"—at least in some sense of the word.
G-Man:
I've got to respectfully disagree with this position, which I see as pretty much a restatement of the Castrol "party line." My problem with it is that it relies upon a stretching of the meaning of the word "synthetic" beyond what had evolved as the reasonably understood meaning of the word.
Sure, there is a very involved process that goes on with the "hydrocracking" of oils, and yes, it is more than just traditional fractional distillation that produces "traditional" oils. But the fact remains that the process is performed upon crude lube stocks that still contains the coctail of hundreds, perhaps thousands of trash compounds that are inevitably a part of crude oil, and which cannot be economically removed, at least not completely. So sure, you get some "synthesized" molecules in a G-III, but you're also getting the soup of unwanted oddball compounds (less most of the wax) that are always a part of a dino oil.
Group-IV and above don't have this problem. Yes, they start with a petrochemical too (ethylene gas, for the most part). But ethylene gas is an isolated homogenous compound that is not "tainted" with the potpurri of unwanted junk that even a good dino lube stock brings to the hydrocracking process. The result is a pure, undiluted stock of PAO molecules tailored to just the lubricating task for which it is designed.
Yes, it looks like most G-IIIs do fine in routine use, but to me, that's not the point. What I really don't like is Castrol's abuse of the term "synthetic." Interpret it as you will, but you've got to admit that the "average Joe" who reaches for a "synthetic" oil probably does not think he's getting what's truly a dino lubestock based product. If Castrol wants to be honest and fair about this, they need to cut the price to reflect true production cost, tell the WHOLE truth about their products, or perhaps even both.
[ May 11, 2004, 09:45 AM: Message edited by: ekpolk ]
