Posted by Alan Bowes on May 13, 1998 at 00:37:34:
In Reply to: Re: Synthetic Oil posted by PL Brand on May 11, 1998 at 12:20:31:
Hi Paul,
Well, as to the molecular size issue, I'd have to research that before I could respond intelligently. I have read that a lubricant's characteristics owe as much to uniformity of molecular structure and the way that the molecules chain together as they do to molecular length, but I'm not a chemist and I'd have to do more reading.
I've heard that the 5W-50 Syntec has a higher pour point temperature than some synthetic 15W-50 oils, so perhaps at Minnesota winter temperatures (at least on an unusually cold winter morning), the 15W-50 might actually flow better. It doesn't get that cold here in Salt Lake City, although it can dip below zero now and again. The Castrol 5W-50 seems to flow very easily at low temperatures (at least at Salt Lake's low temperatures) and when I start a cold engine, the oil pressure comes up right away. It also has excellent viscosity characteristics at full operating temperature. My hot idle oil pressure stays comfortably high. I like the Syntec quite well as a year-around oil.
To tell the truth, I've read SO MANY conflicting reports on motor oils that it's really hard to tell who to believe. I've seen a couple of references, for example, where the Syntec didn't do as well as certain other synthetic oils in the four-ball wear test, but I've seen other reports where it did better than a bunch of other synthetics! So which reports are correct? The problem is that the majority of these references provide either second-hand data or leave out important factors that might help one decide.
For what it's worth, Syntec exceeds ILSAC GF-1 and GF-2, European ACEA A3-96 (5W-50) and A1-96 (10W-30), all car and light truck manufacturers' warranty requirements where the top-end API SJ or SH ratings are recommended, etc.
Supposedly, Syntec (and other synthetics) have been improved in recent years to enhance high-temperature shear characteristics, reduce volatility, improve compatibility with seal materials, reduce ash, etc. etc. Since they're always changing the formulations, it's hard to tell what reports or tests were based on which formulation. There never seems to be enough data, or data about the data.
All in all, though, the Syntec has performed very well for me over the last few years, and I've heard many favorable reports about it. But is it better than other oils? Who knows? One thing that I'm planning to check out is ash levels and volatility. The higher-volatility oils are not necessarily worse, but they may require a shorter oil change interval, since the ligher fractions can evaporate more quickly, leaving a higher-viscosity oil behind. However, I suspect that even the worst of the synthetics will still be noticeably superior to the non-synthetics. Ash levels would be of more concern, even though they are actually quite low as oils go.
There are also some new 0W-something weight oils coming onto the market that look very interesting, with a "new generation" formulation that is supposed to make everybody deliriously happy. Like I said, I'll have to do some additional homework.
Alan