When I was young, a long time ago, I bought a 64 Dodge that had a Poly 318. It used oil. I tried all kinds of oil at the time, all the big names, and then I tried Valvoline racing 20w50. That engine started burning less oil and eventually only burned less than a quart between changes, at 3,000 miles. I put over 100,000 miles on that car and it was running fine when I sold it to buy the 64 Barracuda. No idea why, I was not into building engines till the 64 Barracuda. I have tried most oils over the years, I remember trying a light weight Mobile 1 when it came out with all their claims. Put it in the 273 and ran it hard. I didn't like the hot idle oil pressure and the way the engine sounded. Drained it right out, after that drive, and went back to Valvoline Racing 20w50. I run Valvoline synthetic 10w30 in the three 5.7 Hemi's we have now. Both the Chrysler and Chevrolet Racing manuals state that straight 30 oil will cause the least wear of any oils. That may dated now. Chrysler Racing also stated that they tested synthetic oil and saw no benefit. As for ZDDP, it is my understanding that the zinc can clog catalytic converters so our "brilliant" leaders have banned it from the latest SAE oil grades. I have no idea what the oil companies have replaced it with. However if your engine does not burn oil, the catalytic converter will not clog? I have a 96 ACR Neon with 250,000 miles on it. I ran either Valvoline Racing straight 30 or 20w50, that have plenty of ZDDP, in it it's whole life. I still have it and it runs like new and has the original catalytic converter. So, I recommend good oil with ZDDP conventional or synthetic for flat tapped cammed engines and change it more often than the recommended intervals with a good filter. I also know you have to do what you need to do, but cars are an expensive item and the cost of good oil is relatively cheap. I won't tell you what good oil is, there are many out there.
