http://www.lnengineering.com/oil.html
> Beware of ZDDP boosters and concentrates being sold under various names. These
> products should truly only be used at time of break-in or not at all if a
> fully-formulated break-in oil is used. I haven't tested every one of these
> products, but one thing is very obvious to me. Every product previously sold
> to boost ZDDP, be it STP or EOS, always had roughly an equal amount of
> detergents to offset the affect of ZDDP in reducing the TBN of motor oil. Most
> of these ZDDP concentrates omit detergents altogether or use over-based Ca
> detergents known to reduce the efficiency of the anti-wear properties of the
> oil! Just like you need more Zn and P in an oil that has more detergents, you
> also have to have additional detergency because of the breakdown of ZDDP in
> peroxides and its interaction with combustion byproducts to form sulfuric
> acid. Knowing the right balance is something best left to the oil
> manufacturers and their chemical engineers. More acid, will increase the oils
> TAN, and will lead to corrosive wear of bearings. For once, I will have to say
> that more is not better, especially in this case. EOS and STP are decades old,
> and proven products that work synergistically with your existing motor oil and
> were never designed to boost the Zn and P more than 100-200ppm - unlike some
> recommendations to run double the ZDDP, in excess of 2000 ppm, which can lead
> to increased wear! It is not only the level of Zn and P that is important, but
> also starting with an oil that meets the ACEA A3/B3 standard would assure a
> starting TBN of 10 or higher and with similarly higher HTHS viscosities will
> also give you greater protection too. If you do choose to use these products,
> you must do used oil analysis to determine drain intervals and monitor overall
> TBN retention and ensure that the TAN increase does not lead to increased
> bearing wear! Too much ZDDP can also foul spark plugs and oxygen sensors, not
> to mention plug EGR valves and the catalytic converter. Additionally, lack of
> testing of these ZDDP boosters compared to fully formulated oils intended for
> racing or for older engines or even against SM-rated oils side by side do not
> instill confidence in their performance, or at least at the time this was
> written.
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