4 1/2 or 5 quarts of oil with 1/2 quart of ZZDP?

I formulated engine oils for Chevron for 18 years. The issue with new oil for passenger cars (called PCMO, Pass Car Motor Oil) is that the OEM's are concerned about Cat Convert poisoning. The Phosphorus in ZnDTP (Zinc DithioPhosphate) is a poison to the metals in the Cat. However HDMO (Heavy Duty Motor Oil) has the right level of ZnDTP to let cams last. If you get brands like Chevron Delo 400, Shell Rotella T, or other oils with the API CJ-4, CK-4 classification along with API SN or SP. The C is for Commercial, and the S is for Service (old term). Oils meeting both classifications have at least 12 millimoles Phosphorus (chemical way to say concentration). PCMO's have about 6-8 millimoles. I have used Delo 400 in everything from a 426 Hemi to my 340 that I have had for 53 years. Got over 220,000 miles on a Jeep GC 5.2L and the engine never burnt any oil. 3000 mile oil changes help too.
WalMart has the HDMO at a good price (although recent price increases have hurt!)
Use SAE 15W-40 or try to get SAE 10W-30, but that may be only from a commercial oil jobber.