Very interesting point. Would be nice to use amsoil again and by the way I did notice the 5W50 was like snot when I poured it out of the bottle. Whats your opinion on the 5W40 Redline since it is an SN oil?
The higher ZDDP content in Amsoil AMO 10W-40 will not harm the cats anymore than low ZDDP found in Motorcraft 5W-50. AMO has a very low NOACK (evaporation) about 6%. Motorcraft is ~11%, more than 50% higher. More evaporation means more additive is lost to the intake, and eventually the cats. AMO doesn't have 50% more ZDDP than Motorcraft. See where I am going with this....