Since synthetic oil makes my Limited rattle like crazy I switched to dino oil to quiet things down. In that vein I switched to Valvoline VR1 Racing oil because I've read so much positive about it here. After 900 miles I put on my readers and read the bottle where it says do not to use with catalytic converters. Oops. Didn't know that part, lol. Quick oil change to regular Valvoline M/C dino oil and all is well. Live and learn.

 

The VR1 has a high zinc and phos content that has been claimed to be harmful to catalytic converters. Yeah maybe after 100k miles the zinc and/or phos may render it ineffective, or nothing may happen to the cat at all. Any oil with those additives at those concentrations could do the same. Many guys look specifically for those oils that have the high zinc concentrations to use in their motors. Some cam manufacturers specifically recommend those oils to use as they protect the lobes and lifters much better.

 

Zinc in the oil was a good thing until the EPA decided they did not like Zinc.