Quote: 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.
Garth
What does "too much detergent" do to an old engine? I can see where adding a high detergent oil to a crusty, carboned-up old engine might be bad, but I wouldn't think most enthusiasts are running highly sludged old engines. Most will have been rebuilt sometime in the last 20 years, and are well maintained.
Detergents affect the surface tension of the oil. When the engine is shut off a high detergent oil will run off surfaces quicker than a low detergent. Picture rain water running off freshly waxed paint compared to clinging like a sheet to unwashed paint.
That means a camshaft is likely to be dryer upon startup, because more of the oil has dripped off.
That's the only downside to diesel oils, they are some of the highest detergent oils available. However, the zinc/phosphorous tends to bond with the metal itself, so it may not, should not, be an issue.
