In any automotive lubricant, there can be consideration of cost/effectiveness issues.
I suspect that ANY dino oil, at least up to the SL rating, is far superior than even the best oil from the late 1960s and early 1970s (when additive package technology and viscosity improver technology began to allow for the "super oils" which were in the 10W-50 and 20W-50 viscosity ratings, up from the prior "ceiling" of 10W-30 and 10W-40).
In those days, the "Motor Severe" (or MS) rating was the highest API rating. In the 1980s, other oil rating groups in Europe and Japan came out with rating methods which affect THEIR engine technologies, too. And THEN things got a little tricky to decipher and really know what's going on . . . whic brings us up to more recent/current times.
From the many postings on
www.bobistheoilguy.com forums, it appears that "GF-4" is "the evil rating" which has resulted in the decreased zinc levels, although most every "SM" oil also meets "GF-4" ratings. GF-4 is typically a gasoline engine rating and not a diesel engine rating.
The latest diesel (designed-for) oils are also "SM", but don't have to be concerned with the "GF-series" ratings/approvals. Previously, these same diesel oils were "SL" oils.
Around the time of the Buick Centennial Meet in Flint, there were comments about use of synthetic oils in vintage vehicles. Many reported no problems of any kind, including issues related to oil consumption.
Initially, synthetic oils were mainly used in climates with really cold temperatures (including Antartica and similar) where the engines could not be turned off once running (or the oil would congeal at the lower temperature), so they were more "application/environment specific" in nature. There were only a hand-full of companies that made synthetic oil for the masses back then . . . which changed in the early '70s with the Mobil1 product.
We knew of the advantages of synthetic oil in extreme applications, but expense usually didn't justify it for everybody. As things have progressed, there are still advantages over dino oils, but the quality of dino oils has increased markedly in that same time (usually driven by OEM specs of vehicle manufacturers).
As the original issues of reduced zinc levels (and responses from cam manufacturers, as Competition Cams) happened a few years ago, much of the information still out on the Internet is somewhat dated. The orig recommendation by CompCams was to use either Rotella T (diesel-spec oil) or synthetic oil. Now that Comp and other cam manufacturers now have their own lines of oil additives to address the lower zinc level issue, you'll probably find different recommendations on their websites now.
Be that as it may . . .
I know of people who have and are using Mobil 1 with 3000 mile change intervals. If they can afford that (and the newer cars it's going into), fine with me . . . their money, not mine. Still, seeking out an "SL" and "non GF-4" oil can be a little tricky.
Lately, I've been looking at the Volkswagen diesel forums for oil issues. VW has their own approvals for motor oils, as Mercedes and BMW also have. The 5W-40 VW-spec synthetic oil is "SL" rated and not GF-4 rated, for example . . . and is available at VW dealers and in Castrol SynTech. Just something I found out about, or rediscovered. This particular oil is "European oil" and imported into the USA.
Still, judgment calls are necessary. Thanks to Jim for posting the Mobil oil information link!
Enjoy!
NTX5467
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