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Zddp

AUSMHLY

Obi Wan
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I'm sure this topic of adding ZDDP has come up many times.

I'm currently using Castrol GTX 20w-50 in the engine and tranny, BJ8.
I believe Castrol has lowed the zinc and phosphorus level in this oil.

I've read we should add ZDDP to the Castrol GTX 20w-50 for this engine (any engine with flat tappets lifters) which takes about 6 quarts.
ZDDPlus directions say, add entire contents of bottle (4 oz) to a 4 or 5 quart oil change to restore ZDDP specs to SF levels.
Being I don't know how much ZDDP is in Castrol's oil, what's your thought about adding 4 oz?

Should ZDDP be added to the transmission too? I assume not, but learned assuming is not always correct.

For all the Castro GTX 20w-50 guys, what ZDDP product are you using and how many oz are you adding?

FYI, Valvoline conventional oil 20w-50 for the engine, has the correct amount of ZDDP.

Your thoughts?

http://zddplus.com
A0E43CB3-1C26-46BF-A740-350D3E4061E6.jpeg
 
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Bob_Spidell

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re: "Should ZDDP be added to the transmission too?"

Interesting question.

Answer# 1 is "It couldn't hurt, as engine oil was and is recommended for gearboxes/ODs, and AFAIK ZDDP was added to engine oils starting sometime in the 1950s."

Answer# 2 is "It isn't needed, as I don't think you'll see the pressure/shear forces in a gearbox/OD as you will on tappet and cam lobe surfaces."

Safe to say, IMO, if you're using a decent engine oil you don't need to add any. Gear oils, from GL-1 to GL-5, have 'EP' (Extreme Pressure) additives--some sort of sulfur compound, why they stink--necessary for the shear forces found primarily in hypoid gears (i.e. differentials). Note EP additives can supposedly 'attack' brass/bronze components--e.g. thrust washers--but I've used it for years and never noted any problem (David Nock says it turns the bronze thrust washers in the diffs blackish, but otherwise doesn't cause problems).

If I've got the story straight, ZDDP was initially used as a detergent, then the protective qualities were discovered (similar to tetra-ethyl lead, which was added to resist detonation and raise octane rating of gasoline, then the exhaust valve protection was noted).
 

Keoke

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Just use any good racing oil and your ZDDP will be correct.

VR1 is a good choice. I have run the same VR1 engine oil in my tranny so when I travel I only need one kind of spare oil in the boot.
 
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