Oil and ZDDP

[secondchance]

When I read the thread titled "which oil do you use in the beast" I started thinking about this ZDDP level and it's possible implication on our LT5s.
Owner's manual and FSM for 94 states "SH" rating for the LT5.

According to Marc Haibeck, his reasoning behind recommending Amsoil AMO 10W40 (phosphrus .125% and zinc .138%) is due to current Mobil 1 5W30 and 10W30 with SM designation having reduced level of phosphorus (800 ppm - .08%) and zinc (900 ppm - .09%).

Upon search there are a lot of pre 1990 car forums where concerns are being expressed and even Mobil seems to acknowledge these concerns to a point of recommending their 0W40 or 15W50 racing oil. Some are resorting to motor oil intended for diesel or turbo diesel motor for this reason.

I for one, do not care to run around town or resort to mail order and pay $8 for a quart of oil. Quite frankly I have been using Moil 1 since 1985 and I can get them for $34 a six pack at local Costco. Also, I appreciate the fact that I can run into Moil or Exxon and get a quart in a pinch.

Then, I ran into this product called ZDDPlus. This seems to be ZDDP (zinc dialkyl dithio phosphate) concentrate being marketed to address reduction in ZDDP in most readily available motor oil reformulated to meet concern over catalytic converter longevity possibly at an expence of ignoring needs of older cars.

Based on ZDDPlus calculation comparing phosphate and zinc level boost relative to other similar products, I calculated one 4oz bottle when mixed to 8.5 quarts (because that's what gets changed and for the first application a little extra would be needed) will boost phosphate by 616 ppm and zinc by 873 ppm.

When added to Mobil 1 5W30 or 10W30 with phosphate 800 ppm and zinc content of 900 ppm resulting mix will be 1415 ppm and 1773 ppm respectively. Now, ZDDPlus recommends adding one 4oz bottle to 5 quarts but based on my calculation one bottle would be sufficient to end up with a brew w/ slightly more levels then the Amsoil AMO blend.

As for the cost, I bought 3x4oz bottles for $25 and free shipping on ebay.

Based on my quick review of web posts, perhaps not as severe as ohv high performance engine w/ after market cams and springs but I do feel uncomfortabe that SM grade I have been using in my car has deficient level of zinc and phosphate then what was specified for our LT5.

For this reason I will be adding a bottle of ZDDPlus in the crank case. But, just in case, I wanted to post this and get your reaction to my logic and decision.

Some useful websites that helped me whether I should be concerned and also helped me with calculation:

http://www.zr1specialist.com/HAT%20W...5%20Engine.pdf
https://www.mobiloil.com/USA-English...duct_Guide.pdf
http://www.crower.com/dl/ZDDP_clr.pdf
https://www.mobiloil.com/USA-English...ssic_Cars.aspx
https://www.mobiloil.com/USA-English...t_Engines.aspx