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Has anyone read a clear and understandable explanation of why ZDDP is favored in oils for high contact pressures, but MoS2 is favored in greases?

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MoS2 with particle sizes in the range of 1–100 µm is a common dry lubricant. Few alternatives exist that can confer the high lubricity and stability up to 350 °C in oxidizing environments. Sliding friction tests of MoS2 using a pin on disc tester at low loads (0.1–2 N) give friction coefficient values of <0.1.
Molybdenum disulfide is often a component of blends and composites where low friction is sought. A variety of oils and greases are used, because they retain their lubricity even in cases of almost complete oil loss, thus finding a use in critical applications such as aircraft engines.

Examples of some diverse applications of MoS2-based lubricants include two-stroke engines (e.g., motorcycle engines), automotive CV and universal joints, ski waxes,[10] and even some bullets.
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The main use of ZDDP is in anti-wear additives to lubricants such as greases, gear oils, and motor oils, which often contain less than 1% of this additive. It has been reported that zinc and phosphorus emissions may damage catalytic converters and standard formulations of lubricating oils for gasoline engines now have reduced amounts of the additive, though diesel engine oils remain at higher levels. Crankcase oils with reduced ZDDP have been cited as causing damage to, or failure of, classic/collector car flat tappet camshafts and lifters which undergo very high boundary layer pressures and/or shear forces at their contact faces, and in other regions such as big-end/main bearings, and piston rings and pins. Roller camshafts are more commonly used to reduce camshaft lobe friction in modern engines.

From
http://en.wikipedia.org/wiki/Molybdenum_disulfide#Petroleum_refining

http://en.wikipedia.org/wiki/Zinc_dithiophosphate

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Thanks for posting this!

I use the Comp additive with 10w30 Valvoline. I suppose you would divide those numbers by the number of quarts to compare to the others?

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I'm wondering too.

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Does anybody use this:

http://www.zddplus.com/

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I've used this stuff for a few years now on my engines with the high spring rates and agressive lobes...So far so good.. .I guess if nothing flies apart it's working... ..Seriously though I use it in addition to a high zinc oil so mabe it's overkill mabe not...I wait until it's on sale and snag a bunch of them...

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This is some really good information. I noticed you did not test the Joe Gibbs brand oil. I would really have been interested in that as I am currently using the HR series in my modified 440.

A couple of years ago, I was fortunate enough to attend a presentation put on by one of the reps from Joe Gibbs oil, Lake Speed Jr. It was a very good presentation highlighting the evolution of the car oil industry. The one comment I recall is the modern oils have too much detergent in them today for our older muscle cars. Even with the addition of the ZDDP product, there is nothing you can do to remove the high level of detergent. I, like most of you was looking into adding the ZDDP into my old cars but after this, I will only use something with the right combination of additives. For now, it happens to be Joe Gibbs oil. I have way too much invested in the modified motor to risk the oil side, even if it costs more.

Garth

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Does anybody use this:

http://www.zddplus.com/

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I've used this stuff for a few years now on my engines with the high spring rates and agressive lobes...So far so good.. .I guess if nothing flies apart it's working... ..Seriously though I use it in addition to a high zinc oil so mabe it's overkill mabe not...I wait until it's on sale and snag a bunch of them...

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This is some really good information. I noticed you did not test the Joe Gibbs brand oil. I would really have been interested in that as I am currently using the HR series in my modified 440.

A couple of years ago, I was fortunate enough to attend a presentation put on by one of the reps from Joe Gibbs oil, Lake Speed Jr. It was a very good presentation highlighting the evolution of the car oil industry. The one comment I recall is the modern oils have too much detergent in them today for our older muscle cars. Even with the addition of the ZDDP product, there is nothing you can do to remove the high level of detergent. I, like most of you was looking into adding the ZDDP into my old cars but after this, I will only use something with the right combination of additives. For now, it happens to be Joe Gibbs oil. I have way too much invested in the modified motor to risk the oil side, even if it costs more.

Garth

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What does "too much detergent" do to an old engine? I can see where adding a high detergent oil to a crusty, carboned-up old engine might be bad, but I wouldn't think most enthusiasts are running highly sludged old engines. Most will have been rebuilt sometime in the last 20 years, and are well maintained.

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This is some really good information. I noticed you did not test the Joe Gibbs brand oil. I would really have been interested in that as I am currently using the HR series in my modified 440.

A couple of years ago, I was fortunate enough to attend a presentation put on by one of the reps from Joe Gibbs oil, Lake Speed Jr. It was a very good presentation highlighting the evolution of the car oil industry. The one comment I recall is the modern oils have too much detergent in them today for our older muscle cars. Even with the addition of the ZDDP product, there is nothing you can do to remove the high level of detergent. I, like most of you was looking into adding the ZDDP into my old cars but after this, I will only use something with the right combination of additives. For now, it happens to be Joe Gibbs oil. I have way too much invested in the modified motor to risk the oil side, even if it costs more.

Garth

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What does "too much detergent" do to an old engine? I can see where adding a high detergent oil to a crusty, carboned-up old engine might be bad, but I wouldn't think most enthusiasts are running highly sludged old engines. Most will have been rebuilt sometime in the last 20 years, and are well maintained.

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Which Rotella T? Synthetic or Dino oil?

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Oops. I just checked and my previous response was incorrect. The Rotella that was tested was the synthetic T5 oil.

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Does anyone use diesel oil in their classic?

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Does anyone use diesel oil in their classic?

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Yep. 15-40 in the Duster, and in the 79 van. I even run the 10-30 semi syn in my 93 Corolla.

10-30 should be fine for most applications. I had run the 15-40 in the others because I got a killer buy on it for the Cummins which takes 3 gallons.

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Thanks for this - when you read the ZDDPlus literature they warn against using diesel oil because of the detergents in the oil.