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Oil and ZDDP

Technical issues not related to a DLOC car marque, eg tyres, ethanol, other car makes, etc. and legal, political and insurance
Phillmore
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Oil and ZDDP

Post by Phillmore »

Assuming we agree that this Zinc additive is beneficial to our engines, which oil manufacturer do we think offer the best all round multigrade with sufficient ZDDP to minimise wear and maintain good oil pressure?
Andy

1954 Conquest Mk1, 1956 Conquest Mk2, 1957 Conquest Century Mk2, 1955 Austin A90 Westminster

Phillmore
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Re: Oil and ZDDP

Post by Phillmore »

Has anyone used Penrite classic light 20/60? the spec seems pretty good.
Andy

1954 Conquest Mk1, 1956 Conquest Mk2, 1957 Conquest Century Mk2, 1955 Austin A90 Westminster

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marchesmark
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Re: Oil and ZDDP

Post by marchesmark »

I have used Penrite products for years, the Classic Medium in my Bentley S3 and Shelsley Medium in the Daimler. I find them very good, if a bit expensive. I did not like their Steering Box semi fluid grease though, it didn't do what it was supposed to do, and I found Millers Worm Steering Box oil better. I also use Morris Oils from Shrewsbury, their stuff is good as well.

Mark

Chris_R
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Re: Oil and ZDDP

Post by Chris_R »

Phillmore wrote:
Mon May 15, 2017 9:38 am
Assuming we agree that this Zinc additive is beneficial to our engines, which oil manufacturer do we think offer the best all round multigrade with sufficient ZDDP to minimise wear and maintain good oil pressure?
It all depends on the level of wear in the bearings in the engine. The original specification was more than likely for a SAE 30 or SAE 40 grade oil so if your engine is in good condition you could easily choose something like a 10W-40, a 5W-40 or a 0W-40, all of which will match the original grade specifications. A 0W, 5W or 10W will give better cold start performance than a 20W and will circulate through the galleries and bearing more quickly and effectively than a 20W.
You don't need huge oil pressures, what you really need is good oil flow. About 10psi per 1000 rpm is really the minimum you should aim for if you are measuring the pressures. If your engine is a bit worn (or perhaps more than a bit) then a -40 oil might be too thin (remembering the original specification was for a 30 or 40 grade of oil) and you can go to a -50 or even a -60 oil. These will be more resistant to flow and so will stay better in worn bearings than a -40 grade oil would stay. Ultimately not even a -60 grade will be enough and then it will be time for a crankshaft regrind.
A typical -40 oil will have a viscosity rating of about 14 at 100c. A -50 oil might be 17.5 and a -60 oil will be of the order of 26. Thicker is not always better, thicker gives more resistance to flow and in the bearings more friction and can lead to higher heat levels although at relatively low engine revs this is not really very likely.
Much is written about the reduction of ZDDP in modern oils. This is only partly true. In a select collection of oils, those of -20 or -30 multigrade grades, i.e. 0W-30, 5W-30 or 0W-20, ZDDP is restricted to a minimum of 600ppm and a maximum of 800ppm. It hasn't been removed altogether, just reduced to those levels. How much do you need? Here again, more is not always better. Break in for flat tappet cams is recognised to need above 1200ppm but if you go above 1400ppm you can get increased longer term wear and above 2000ppm it will actually start to attack the underlying steel. Other oils, such as 10W-40, 5W-50, 10W-60 and others with -40, -50 or -60 are not restricted in ZDDP content whether they are mineral, semi-synthetic or fully synthetic. In the 1950s, ZDDP was at a level of about 800ppm. In the '60s and '70s it was increased to higher levels, not to counter wear but as a cheap anti-oxidant in the newer higher pressure engines in which the oil would otherwise turn to sludge and become too thick to pump. As other anti-oxidants were then introduced, the levels of ZDDP were reduced back to just over the 1950s levels. What is the ideal level? No one really knows for sure. In the 1950s and again in the 1970s General Motors experimented with levels of 600ppm and found no adverse effects.
I like Mobil oils and would choose either Mobil Super 3000 5W-40, Mobil Super 2000 10W-40m, Mobil 1 5W-50 or Mobil 1 10W-60 depending on what I needed. All of these have about 950 - 1,000ppm of ZDDP.
Personally I would avoid the so called Classic Oils that are made to old and now obsolete standards. Because those standards are obsolete, there is in effect no standard that is being applied or tested for these oils. You only have the word of the company selling it that it meets some sort of standard that is now obsolete and not maintained whereas oils made to the newer and current standards must adhere to those published standards.

Phillmore
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Re: Oil and ZDDP

Post by Phillmore »

Thanks Chris for that most comprehensive answer. So in view of the modern oil standards you mention, would you actually recommend a higher spec semi synthetic oil rather than a classic oil? The Penrite Classic Light 20/60 contains 1060ppm ZDDP and Millers Golden Film 700 ppm.
Andy

1954 Conquest Mk1, 1956 Conquest Mk2, 1957 Conquest Century Mk2, 1955 Austin A90 Westminster

Chris_R
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Re: Oil and ZDDP

Post by Chris_R »

Synthetic oils will always outperform mineral based oils which includes semi-synthetics where there isn't a specific standard governing the blend. That said, very low use cars can get a build up of waxes and sticky residues in the bores and in the rings from the use of synthetic oils because they never get hot enough to evaporate condensations that build up in the oils which then gets exposed to very high temperatures when it is splashed on the cylinder walls. For those it is probably better to use a good mineral based oil and change it annually. You could probably use either of the ones you mention with little problem. ZDDP works by heat and pressure causing a reaction between the zinc and phosphorous and the underlying steel surface to produce a glass like surface across the steel. Once this glass like surface has been created you can't make it thicker, there isn't any more exposed steel to react and so having more isn't of any benefit but levels like that won't do any harm.

Phillmore
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Re: Oil and ZDDP

Post by Phillmore »

I'm sure there isn't a simple answer to this simple question but . . . . which type of oil (mineral or SS) would maintain better pressure when hot?

We took the Austin to the Black Mountains at the weekend to pick up an old sewing machine that my wife had purchased on ebay (they need their hobbies too)!The manual states 60psi on start up, 55psi running when hot and 25psi tickover hot. I get 60psi on start up which drops to 45psi when properly warmed up and 25psi tickover so not too worried. What I have noticed is that on deceleration when hot the 45psi rises to 50psi?? My only theory is possible oil frothing under load?

I like gauges but sometimes ignorance is bliss and with one eye on the oil gauge and the other on the temp gauge it doesn't leave much for the road ahead! ;)

About ten years ago I was talking to an owner of a Conquest at a classic car event at llandrindod. He said he'd fitted an oil pressure gauge but was so alarmed by the readings that he promptly removed it! :D. I suppose with just a green light there isn't much to worry about (assuming it goes out and stays out of course)!
Andy

1954 Conquest Mk1, 1956 Conquest Mk2, 1957 Conquest Century Mk2, 1955 Austin A90 Westminster

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theoldman
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Re: Oil and ZDDP

Post by theoldman »

Andy,

Daimler have always worked on "lots of oil but at low pressure" - the Conquest relief valve unit is set to blow at 40psi!!! Running hot, 30psi is a good reading.

I did tweak the LJ valve to give me 50psi at start up and 35 - 40 running hot.
Normal for Norfolk

Chris_R
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Re: Oil and ZDDP

Post by Chris_R »

Correct, lot's of oil is what is needed, not oil pressure although you do need some pressure to get the flow and the required quantity of oil. All you do by increasing the pressure is increase the load, you don't actually get any more oil into the bearings which is mainly where that pressure reading comes from. Although a small increase will not do much harm and it will probably give you greater peace of mind! The oil pressure that you can read on a gauge is not what is supporting the crankshaft journals in the bearings, it is much more complicated than that which of course Daimler knew and why they made their statement.

Andy:
You are correct, there isn't a simple answer. The answer is neither. Or both. If you get a 15W-40 mineral oil, a 10W-40 semi-synthetic or a 5W-40 fully synthetic, because they are all -40 grade and their hot viscosity will all be very similar, the resulting oil pressure should be the same.
There should not be any frothing. Oil additives prevent that and in case, frothing implies air mixed in and that is the last thing you would want as then you would not have enough oil present to prevent metal to metal contact.
The change in pressures that you observe are the result of the oil thinning as it gets hot and the result of the resistance to the flow of that oil through the engine, mainly at the crankshaft bearings. If you observe a slight increase in pressure on deceleration I would suggest that is because you have lifted the load off the crankshaft by not applying power, but the engine is still turning at the same (similar) speed and therefore pumping as much, and there is a slight increase in resistance to the flow as a result, probably because there is a slight difference in crankshaft position inside the journals.
The stated 60psi on startup will be the pressure where the relief valve opens to allow pumped oil to bypass back to the sump. When cold the oil is far too thick and creates a high resistance to the flow from the pump which is why you always get a higher pressure on startup and it needs heat to thin it to the correct level for the best efficiency in the engine. That's why decades ago people used to put little heaters under the sumps in winter and that's why today you have the multigrade 0W, 5W to 20W ratings. You get an oil that behaves in two ways simultaneously. You have a (relatively) thin oil at low temperatures and a (relatively) thick oil at high temperatures. A 10W oil would be far too thin when hot and a -40 or -50 would be far too thick when cold. So by engineering with the use of polymer additives they control how the oil changes and you get a liquid that behaves one way when cold, the 10W rating, and a different way when hot, the -40 or -50 rating.

Phillmore
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Re: Oil and ZDDP

Post by Phillmore »

Thanks Chris, so when you explain the slight increase in pressure under deceleration being due to the slight difference in crankshaft position, what we are actually talking about is probably wear in the crankshaft bearings? I thought that some of the additives in more modern oils were added to reduce frothing. I think the last oil I put in the A90 was Halfords Classic which probably isn't the best classic 20/50.
Andy

1954 Conquest Mk1, 1956 Conquest Mk2, 1957 Conquest Century Mk2, 1955 Austin A90 Westminster

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