This is some really good information. I noticed you did not test the Joe Gibbs brand oil. I would really have been interested in that as I am currently using the HR series in my modified 440.
A couple of years ago, I was fortunate enough to attend a presentation put on by one of the reps from Joe Gibbs oil, Lake Speed Jr. It was a very good presentation highlighting the evolution of the car oil industry. The one comment I recall is the modern oils have too much detergent in them today for our older muscle cars. Even with the addition of the ZDDP product, there is nothing you can do to remove the high level of detergent. I, like most of you was looking into adding the ZDDP into my old cars but after this, I will only use something with the right combination of additives. For now, it happens to be Joe Gibbs oil. I have way too much invested in the modified motor to risk the oil side, even if it costs more.
