I should also note--despite the fact that this thread emanated from the reported unavailability of Mobil 1 in the formulation for our cars (15W-50), that a number of other manufacturers make specialty blends for either Classic (sorry Dan, not my word) and or performance cars. These oils didn't exist in present formulation 50 years ago, but they do today to serve the needs of cars that are, well 50 years old...give or take.
Lucas 20W-50 Hot Rod & Classic
Castrol GTX Classic 20W-50
Champion Classic & Muscle 10W-30
Brad Penn Partial Synthetic Racing Oil
Hemmings Motor Oil 10W-30, 20W-50, 15W-50
Classic Car Motor Oil (by D-A Lubricants) 15W-40
Driven Racing Oil
Amsoil Z-Rod (thought they specifically don't list any oil on their selection chart for cars prior to 1980)
Shell Rotella (for diesels, not specifically noted for classic)
Liqui Moly Classic 20W-50
This is not meant as any kind of comprehensive list. But the more you search the more you will find some common "themes" in an oil branded for "classic and or performance cars".
1. Higher levels of ZDDP than for oils for modern cars; basically they are throwbacks to older formulations.
2. Perhaps also recommended for diesels; diesels don't have catalytic converters and thus their oils (like the Rotella) can have higher levels of ZDDP
3. Higher viscosities; you'll see a lot of oils with a -40 and -50, and the winter ratings 15W and 20W. By contrast a lot of daily drivers today specify 5W-30.
4. Racing oils are not generally recommended for street use (read the fine print), certainly not on modern cars. I think that's because in true race use, they are changed frequently and thus don't contain some of the additives that an oil would have that sits in the car for a year or more...and may be hard on some modern emissions gear?
So, you can debate all you want on the needed ZDDP levels, but the oils of 50 years ago had more than the oils of today for conventional use. Thus the "classic" oils were developed to serve the "needs" of older cars.
Since so many of these oils are in the 15W-50 and 20W-50 ratings they may be on to something. If you think that's too high, well there's the ones with -40, and one of the Hemmings has a -30 rating.
All in all, no shortage of available oils no matter whether you want synthetic or conventional, and in a variety of grades. Note also this is a list of oils from the USA. UK, Worldwide, Eurozone may all be different.
Since many of these are "specialty oils" you may not find them over the counter at your local store, but almost all are available by mail order.
