[Hib Halverson]

My LT5 currently has Red Line 10W30 in it. If the oil drain interval comes due before I sell it, I'll switch to Gibbs Driven HR 10W30.

But...oil in general:

For best performance and protection you need an oil blended with a synthetic base stock, such as Red Line's ester base or Gibbs Driven's mPAO base. The Mobil 1 which is widely available in North America uses neither of those base stocks. It's not always easy to ascertain what base-stock with which an oil is blended so, when in doubt, contact the oil vendor and ask.

As for ZDDP, most engine oils sold for high-performance street or street-track have adequate extreme pressure additive packages. That said, the whole ZDDP "thing" with the LT5 is just a myth. Yeah, the LT5 has flat tappets but the load at the lifter/lobe interface is significant lower in the LT5 because of its OHC valve train. OHV valve trains with flat tappets is where you see problems with performance cams, high spring pressure and low (less than 800 PPM phosphorous) levels of ZDDP.

Drain intervals? If you're using good oil, use the oil life moniter but change the filter at 50% and, of course, 0%/ In any event, with ZR-1s which see low annual mileage, change the oil every year or so regardless of mileage.