Appears I can post now!
Here is AMSOIL's relatively new offering for classic cars:
AMSOIL Z-ROD 10w30 Synthetic Motor Oil (Product Code ZRTQT)
(zinc – 1440 ppm, phosphorus 1320 ppm)
The reason an oil like this is important to older cars is that the API has changed the oil specs over the years, and not necessarily in a good way.
Historically, engine oil had phosphorus on the order of 1200 ppm.
From 94-97, the API SH spec allowed up to 1200 ppm phosphorus for 5w30 and 10w30 and didn't address other 30 grade viscosity like 0w30. In 97, API SJ dropped the limit to 1000 ppm, but still did not address 0w30. In 01, API SL kept 1000 ppm phosphorus, but added 0w30 to the spec. In 04, API SM further dropped the limit to 800 ppm, but for the first time set a floor at 600 ppm and advertised that oil's were better. Essentially they were capping how much phosphorus the better oils could have and mandating the lowest amount the cheapest oils must have. The current API SN spec still has the band 600-800 ppm phosphorus.
Unfortunately, phosphorus, along with zinc, in a compound called ZDDP, or or zinc dialkyl dithio phosphate, forms an oil's primary anti-wear additive. The reason behind this is that phosphorus slowly poisons the cats and prevent the catalytic exchange that allows them to function properly. To ensure auto companies could meet the EPA's 100k+ emissions requirements, the API has slowly been dropping the limit on phosphorus.
So, any oil labeled to meet the current API SN spec will be limited to 800 ppm max phosphorus. This impacts how well it will be able to perform in anti-wear, such as might be seen in your bearings under heavy load.
Oil's like the Z-ROD bypass the current regulations and have lots of ZDDP. The Z-ROD is very similar to the racing oil I use:
AMSOIL Dominator Synthetic 10w30 Racing Motor Oil (Product Code RD30QT)
(zinc – 1575 ppm, phosphorus 1474 ppm)
The main difference is that the Z-ROD had enough detergents for 3-5k miles, or one years whichever first, oil change intervals, whereas the racing oil has no detergents and I change it at about every 500 miles of track use. The Z-ROD also has rust inhibitors which may provide benefit to cars that are stored for much of the year.
If anyone is interested in trying AMSOIL, more than happy to get AMSOIL products for forum members at dealer wholesale pricing, about 25% below retail, via the
AMSOIL Preferred Customer Program. Drop me a PM if interested. :cheers:
