View Full Version : Additional Zinc (ZDDP) information

10-17-2008, 11:00 AM
I happened to watch Motorweek on the Speed Channel this mornning and by chance there was a segment on Zinc in oil.

They had as a guest Tom Smith of Valvoline. He provided a comprehensive discussion of zinc in oil, past and present.

History and development:zddp has been used from 1940s - 200 ppm initiallylate 50s 300 ppm1200 ppm in 70sIt functions as antioxidant and anti corrosion. It was well after the 40s before it was appreciated for anti-wear capabilityproblem: phosphorous in Catalytic converters forms a coating counterproductive to the funciton of the catIn 1992 the industry began reducing, to current the current 800 ppm levelHe claims 800 ppm will protect older flat tappet engines, except during the break in phase where 1200 ppm or more is neededValvoline racing has 1200 ppm so a good choiceUnfortunately, if you are like me, you did not know this when you were breaking in your motor. I did as in the past - used Castrol and changed it after 250 miles. So the horse is out of the barn. At some point I will take a lifter out and see what it looks like. My motor now has 5000 miles on it, all with Castrol 10W-30 GTX. I will look up what Castrol currently has. For the time being I am adding ZDDP + from Eastwood to be on the safe side

A search of Castrol's own website reveals concern about zinc but only Syntec 20w-50 as having zinc levels aimed at older cars as shown at http://www.castrol.com/castrol/genericarticle.do?categoryId=82915470&contentId=7032644 which is worth looking at... I could not find zinc levels on their site for their other motor oils so I called their 800 number. A tech guy said they would not release zinc levels to me but that for a classic car application, the GTX would not have sufficient zinc. He went on to say that 20w-50 oils were exempt from the API mandates of low zinc levels and thus their Syntec product could be developed with older cars in mind.


10-17-2008, 11:25 AM
Thanks for the post John. :cool:

10-17-2008, 03:49 PM
I used the Contact Us page and asked about Castrol for classic cars. I got the following response about 4 hours later to my question of zddp levels in GTX :

Thank you for contacting Castrol North America,

Castrol does not publish any formulations or changes in formulations. The
information that you are requesting is considered proprietary.

The latest API SM/ILSAC GF-4 category calls for reduced Zinc and Phosphorus
levels to allow extended catalyst life in current model vehicles. There
appear to be field issues associated with the SM/GF-4 oil's level of
anti-wear in the classic car engines known as flat tappet cam engines. The
current late model passenger car engines are not flat tappet cam engines and
have no reported field issues related to the level of anti-wear chemistry in
the SM/GF-4 oils.

Product Recommendations for Flat Tappet (Solid Lifter) Cam Engines:
Castrol Syntec 20W-50 (Recent reformulation identified by "Recommended for
Classic Cars" text on back label) (min Zn = 0.12 = 1200 ppm)(full synthetic)

Castrol Consumer Relations

Dan Leavens
10-17-2008, 06:27 PM
John thanks very much for this data, as it is very valuable and will print off for the file.

Dano Calgary,Alberta Canada

10-17-2008, 06:31 PM
hi Dano

no guarantee that the requirements of reduced zddp are the same in Canada...


10-17-2008, 06:39 PM
I don't like the 20-50. If you don't accually take the car out and run it almost every day. Things are going to get clogged up in cold weather.

10-17-2008, 08:07 PM
I agree...I live in New England. So my best set up seems to be using 10W-30 and adding the ZDDP+ from Eastwood.


10-17-2008, 08:52 PM
I'm doing the same GTX 10W-30 with ZDDP+.

Even though I'm in Texas, the 20W-50 weight is a little too heavy for my taste on a rebuilt engine.

Good research John.

Dan Leavens
10-18-2008, 11:42 AM
John the requirements of ZDDP are similar up here and with our elevation ( 4200 feet above sea level similar to Denver ) that has to be factored in with the viscosity of oil.

Dano Calgary,Alberta Canada