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Thread: Zinc additive in engine oil?

  1. #1
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    Zinc additive in engine oil?

    Hey all!

    Just a quick question... I did a search and found nothing, so I hope no one minds me asking this question here.
    Anyway, I was wondering if anyone adds zinc to their engine oil when they do oil changes? I read that zinc was phased out around 1994, so that would mean that the oil that the D was designed to use had to have zinc, right? My dad says the zinc helps the cam not to wear out.

    Thoughts?

    Thanks!

    Jacquie V.
    D#4418
    Jacquie V

    81 DMC, manual, grey interior.

  2. #2
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Jethowl View Post
    Hey all!

    Just a quick question... I did a search and found nothing, so I hope no one minds me asking this question here.
    Anyway, I was wondering if anyone adds zinc to their engine oil when they do oil changes? I read that zinc was phased out around 1994, so that would mean that the oil that the D was designed to use had to have zinc, right? My dad says the zinc helps the cam not to wear out.
    You'll have to do some more research but I believe that the recommended oil, Castrol 20W50, still contains a lot more zinc than other motor oils, and is specifically intended for older engines.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  3. #3
    Senior Member skill's Avatar
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    JetHowl, Thanks for asking the question. I'm about to change the oil on mine and I appreciate Dave letting us know this info. Much appreciated, Brian

  4. #4
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    Thanks for the info, Dave!
    I'll look into that. I have never used that type of oil, so I'll definitely check it out. Thanks a bunch

    Jacquie V
    Jacquie V

    81 DMC, manual, grey interior.

  5. #5
    Senior Member Bruce Johnson's Avatar
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    I use Valvoline VR1 in all of my older cars. It's a high zinc oil great for anti-wear.

    Bruce

  6. #6
    Senior Member hmcelraft's Avatar
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    I have done some recent research for an oil for my DMC

    Rob Grady put in an OEM long block for me in late 2012 and I was concerned about the lubrication requirements for an older spec engine. Much has changed in 30 years and I wasn't sure of the impact. Especially as it relates to metal quality and modern machining vs a 30 year old tech new engine. It appeared that zink is an issue although lubrication qualities are much improved with modern motor oils, especially synthetics. In the old engine, with 100,000 miles, was getting coolant into the engine - I believe from a blown lower jug seal - thus the replacement. I had used Valvoline 5W-40 in the engine for many years (say 50,000 miles worth) based on some nominal research. This time I wanted to do more research.

    The additive in oil that includes zink also contains phosphorous - ZDTP or ZDDP. Apparently, among other reasons, zink additives have been reduced in recent years because if the engine burns any oil, it can be a cat-killer. Motor oils in the x-40 and x-50 range are not restricted as to additives, i.e. no zink/phosphorous restrictions. Diesel engines and motorcycle engines tend to have beefier additive packages and possibly more ZDDT and they are usually 40 or 50 weight oils. Fortunate for the OEM DMC motor. My goal was to find a modern gasoline engine oil with the best additive package. I wasn't necessarily looking for a lot of zink as I was looking for the best lubrication with the minimal additives to give me the protection I needed. There are various tests you can look for but unfortunately they are very hard to find. So, I decided to try and find an oil that had a highest gasoline API rating - SN; a beefy additive package qualifying the oil for diesel use (C ranges) which meant synthetic or a synthetic blend - probably.

    I found the following synthetic or synthetic blend oils that met API SN and API CF: (There are others but these seem to be readily available)
    5W-50 Castrol Syntec and Pennzoil Platinum
    15W-40 Valvoline Durablend
    10W-40 AMSOL XL 10w40, Valvoline Durablend, Castrol Syntec, Mobil 1 High Mileage and Shell Helix HX7
    5W-40 Shell Helix Ultra, Valvoline Synpower HST, Valvoline Synpower MST

    After a 1000 mile break-in on Shell Rotella T5 (SM, CJ), I decided to go with Mobil 1 High Mileage 10W-40 (SN, CF) mainly because it was full synthetic at the correct viscosity and it had some additional additives to handle the sealing. Also, Mobil's web page shows it has a fairly high additive package - higher than most and, I can get it at WalMart. I have about 5,000 miles on the engine. Oil pressure is great - engine has very little noise so far. I fully expect to get at least 100,000 miles out of this engine as I did the old one.

  7. #7
    Senior Member
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    An excellent article on zinc in motor oil:
    http://www.healey6.com/Technical/oil.pdf

    I use Brad Penn 20W50 in my D. It's basically the old green Kendall GT-1, made in the former Kendall refinery in PA.

  8. #8
    Senior Member hmcelraft's Avatar
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    Mobil 1 ZDDP

    Mobil 1 High Mileage 10w-40 has 1000ppm of phosphorus 1100 ppm of Zinc. I couldn't find the specs for all of the oils I investigated. Of the ones I did find, the x-40 or x-50 oils all had the higher ZDDP levels.

  9. #9
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    Thanks for all the opinions! This has been so helpful!

    Jacquie
    Jacquie V

    81 DMC, manual, grey interior.

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