Some Oil Info from the people themselves!
 

Thank you for contacting Castrol North America.

Castrol is aware of articles in enthusiast magazines and web- sites, as
well as after-market parts manufacturer discussions concerning GF-4 engine
oils and cam-shaft durability issues in older performance vehicles. Some
consumers suspect the lower level of ZDDP in GF-4 oils may be causing
these failures. Castrol is currently investigating this issue.

If you wish not to use a GF-4 oil in your {Classic car}, Castrol does offer
the following products that contain Zinc at a level that is higher than
the Zinc level found in oils (API SG) marketed during the "muscle car" era
of time:
* Castrol GTX 20W-50 (SL,SM)
* Castrol GTX Diesel 15W-40 (CI4,CH4,CG4,CF4,CF,SL)
* Castrol GTX High Mileage 20W-50 (SL,SM)
* Castrol HD 30 (SL,SM)
* Castrol HD 40 (SL,SM)
* Castrol Syntec Blend Truck 15W-40 (CI4,CH4,CG4,CF4,CF,SL)(Semi-
synthetic)
* Castrol Tection Extra 15W-40 (CI4Plus, CI4,CH4,CG4,CF4,SL)
* Castrol Hypuron S 15W-40 (CI4Plus,CH4,CG4,SL)(Semi-synthetic)

Thank you again for your continuing patronage.

Castrol Consumer Relations
_____________________________________________


The Valvoline VR-1 Racing Motor Oil
• The #1 selling Racing Oil of all time and race track proven.
• Protects against high-temperature deposits for a cleaner engine.
• ZDDP additive provides tough anti-wear protection.
• Enhanced with fricition modifier to improve horsepower.
• Formulated with enhanced anti-foam system.

Zinc amount = 0.14% or 1400 ppm
Phosphorous amount = 0.13% or 1300 ppm

__________________________________________


Shell answers:

"Shell Rotella T Multigrade Oil SAE 15W-40 with Triple Protection Technology, our API CJ-4/SM specification product, typically contains about 1200 ppm zinc and 1100 ppm phosphorous as manufactured."
_______________________________________

Hope this will help some of you!!!!