Marc's article on AMSOIL (some years back) put me on that regime from the first. It's pricy, but just a drop in the bucket compared to the price at the pump for gasoline (is the way I rationalize it...).
Viscosity and Change intervals... A good question; and no doubt varies with synthetic vs dyno, ZDDP levels and other additives, and oh, yeah...DRIVING CONDITIONS (e.g. racing, etc), driving habits, temperatures incl summer vs. winter, etc, etc.
Change intervals? Too often and the benefits in terms of engine wear are small, if any. Too far between changes might save $$ on oil, but cost much higher $$ in wear: again so dependent on how the car is driven. (Better too change it often than not often enough.)
Perhaps the only way to know how good the oil is and how often to change it requires a fairly comprehensive (lab) analysis; several oils over several driving conditions/mileages. The sad thing is, we poor consumers can't look to the oil manufactures for anything resembling truth in advertising. Seems to me, NOTHING related to automotive "stuff" is as rife with marketing hyperbole as oil.
So... what's a poor bloke to do? Personally, I take comfort in the
pragmatic approach by mechanics like Marc Haibeck or Cory Henderson, or Aron, or AES, etc. recommend, having torn down "a few" LT5s and would have a better handle on what works and what doesn't...maybe. SO! Out of all the hype, and what actual data there is available on our LT5's in particular, AND with a keen eye on what the key ZDDP levels were when these engines were being built, is perhaps as good a start as any.
Bottom line:
No prize is given for the longest interval between oil changes or using oil with the lowest ZDDP. But, I have personally witnessed and replaced a cam that was wiped smooth (no "bumps") on Ami's 350 SBC which had been on a diet of 10W-30 Dino oil, "API M" (with the inherent reduced levels of ZDDP due to catalytic converters...which her 69 C3 never had).
So, for better or worse, AND per Marc's recommendation and documentation AND experience with the LT5, I'm using AMO 10W-40 which has ZDDP that nearly matches that available when the engines were built. And, being it is a full synthetic, it has the
extended durability and
viscosity stability (that synthetics are noted for). So, I change it at 5000 mile intervals or at the beginning of the driving season (whichever occurs first). Dom is using diesel oil (Rotella?) on 3000 mile intervals. (to error on the side of safety, I guess).
I recon the great oil debate will not end soon. Armed with the info supplied by Marc and others with regard to what was recommended for the LT5 when it was being built, and what is availabile today (synthetics), is as good a place to start looking as any, I recon. Good luck!
11-20-2014
Re: First Oil Change
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