The most recent repsonse from ZddPlus:
" SO for 4 liters, and using 900ppm phosphorus oil it would take 1 ounce of ZDDPlus™ to bump the sump ZDDP level to the Alfa’s API SG (1200ppm) recommendation.
Regarding the issue of whether the additive package is compatible with ZDDP, it already is: because ZDDP is already in the oil, and you are only changing the amount by 20%. I have heard people outside of the industry theorize about some critical “balance” which can be upset, but there are several realities which disprove this speculation:
1) The level of both ZDDP and detergent declines from the first time you start the engine after the oil change. If the exact level of available chemical was critical, the oil should then stop protecting the engine soon after the change…it does not.
2) The additive package formulators (not the oil companies, the companies that the oil companies buy the additive packages from) publish dosing charts showing how to mix and match the different packages to achieve different results. If the additive manufacturers encourage custom formulations from the stock additives, then…
3) In order to be type approved, every oil must be able to be mixed with any other type approved oil with no dire consequence. Have you ever heard of problems with someone merely mixing two oil types? We have not seen any documented cases of this ever happening. Talk a bout a custom formulation!
Thank you for your continued interest in ZDDPlus™.
Howard Hoyt
Dir. of Engineering
AMI, LLC