Posted by Vaughn [172.69.140.144] on Tuesday, September 29, 2026 at 10:15:46 :
I reached out to Castrol to find out how much ZDDP was in their oil and this is their response. Good oil for the FFPW.
Thank you for contacting Castrol North America.
It is our belief that Castrol makes the finest lubricants available in the world, and our commitment to being the technology leader in lubricants is paramount. We sincerely appreciate you taking the time to share your positive feedback with us. It is always rewarding to hear from customers who enjoy our products and trust Castrol for their lubrication needs.
Castrol GTX Classic 20W-50 is specially formulated to provide outstanding wear protection for classic and collector vehicles, as well as certain racing applications.
This high-performance conventional motor oil is designed for pushrod and flat-tappet engines, along with performance camshaft applications. It contains elevated levels of zinc (approximately 1,400 ppm) and phosphorus to help protect against premature wear, metal fatigue, and engine aging, particularly in engines with high-tension valve springs or performance modifications that generate increased contact pressures and operating temperatures.
Castrol GTX Classic 20W-50 is suitable for use in gasoline-powered automotive engines where the manufacturer specifies an API SJ or earlier performance level and a 20W-50 viscosity grade. It is an excellent choice for many classic and collector cars, muscle cars, hot rods, and race cars.
Important: Castrol GTX Classic 20W-50 is not recommended for use in modern engines equipped with catalytic converters or in applications with wet clutches.
Regarding additive information such as phosphorus, detergents, and other components, Castrol does not publish the complete additive package for our lubricants. Our additive systems and base oil formulations are proprietary and are selected based on performance, protection, and suitability for the intended application. The zinc content is published because it is particularly important for the types of engines for which this product was designed.
Unfortunately, Castrol does not maintain a vehicle recommendation database for automobiles manufactured prior to 1970. For guidance specific to your vehicle from the 1960s, we recommend consulting the original engine manufacturer or a qualified specialist familiar with that engine design.
We have attached the Technical Information Data Sheet for Castrol GTX Classic 20W-50 for your reference.
Thank you again for your interest in Castrol products. We value your patronage and appreciate the opportunity to assist you.
Before you go, could you take 30 seconds to rate your experience with me today? Just click the link:
Consumer Satisfaction Survey � Fill out form
Your feedback really helps us improve and is greatly appreciated. Thank you!
Castrol Customer Relations
1‑888‑CASTROL (1‑888‑227‑8765)
Hours of Operation:
Mon�Fri, 9 am � 7 pm ET
Follow Ups: