Motor oil additives, including ZDDP additives, when tested, have proven to diminish the anti-wear properties of oil. Magazines, web sites, etc. don't often publish the results of such testing .... because the additive companies are advertisers.
You probably remember a decade ago when people were having trouble with cam lobes wearing quickly after a new flat tappet cam was installed. So people started dumping-in a high amount of ZDDP additive to prevent lobe failure. The problem was the additive actually made things worse, it reduced the anti-wear properties of the oil and thus increased the likelihood of cam lobe failure. Side note: I am convinced the problem was insufficient cam lobe taper, strangely happening to the cams sold by a company or companies that marketed retro-fit hydraulic roller cams.
Did you know that when the additive Slick 50 was first marketed, it cost $49.95? Yup ... a slick way to make 50 bucks! Talk about an in-your-face scam. I think that speaks volumes about the entire additive industry. Snake Oil.
The last 2 new vehicles I've purchased were operated on synthetic oil beginning with the first oil change. Both vehicles burned less and less oil through-out the entire period of ownership. The rings seated better and better, which indicates the ring grooves never "carboned-up" and the valve stem seals were still in good shape. The engine internals remained 100% clean, no build-up of anything, no gum, no carbon ... just perfectly clean like it was the day it was assembled. No oil leaks, the seals were in good shape too. The first car went 250,000 miles when it cracked a head due to a coolant pump failure. I drove the second car over 200,000 miles, gave it to my son Justin, he put about another 100,000 miles on it then sold it. The engine was still in new condition, and burning less oil than when I sold it to him. It had gotten to the point that there was no detectable drop in oil level between 5000 mile changes.
Feed a new or freshly rebuilt engine synthetic oil and you'll need nothing else.
