Oil Recommendations
Thought I would ask valvoline as well....here's what they said
"The oil will be 100% compatible with the vehicle, but we would suggest using a lighter weight. The Valvoline VR1 Racing Oil is always produced in an SAE 10w30 viscosity and that is our recommendation for your vehicle."
How much ZDDP is the oil supposed to have for our cars? Chart from the link bad V6 says Zinc/Phosphorous 0.130/0.120 is that enough?
The viscosity of the oil is an engineering decision made when the engine was designed, and is based on factors such as intended RPM range, bearing width/design load/clearance, and climatic conditions.
The same engine put to widely different uses will be specified with two different oils. Merely as an example, a high RPM street engine which needs 10W-30 versus the same engine in a taxicab which spends a lot of time idling and low RPM, which would be designed to use 15W-40 or higher.
In a hydrodynamic bearing like the crankshaft and crankpin bearings, the heat developed in the bearing journals (other than that conducted through the block casting) is entirely due to oil shear. Oil that goes into a bearing at 160°F can exit the side clearance of a bearing at over 500°F when under a heavy load. This is because the bonds between the oil molecules are literally sheared apart as the loaded crank journal compresses the oil film in the hydrodynamic wedge.
There is an optimum viscosity which the engine was designed for which takes all factors into account. If an oil with too high viscosity is operated at high RPMs, the oil will degrade quickly in the bearings as it is heated near it's decomposition point. Racing engines do this every time they are run, but it does not matter, since the oil is dumped so frequently.
The oil for street engines needs to be more carefully chosen, since the oil change interval is so long, even at 3000 miles. It is this factor that makes choosing oil not trivial.
Here are some oil facts. True racing oils with low detergent are entirely unsuited to street engine use, since the acids which form in the oil will accumulate and attack internal engine parts.
Racing oil of high viscosity are not appropriate for street engines which are expected to be run at high RPMs. This is the reason Valvoline suggested that 20-50 is not so suitable for the GN engine especially with normal oil change intervals. I know that lots of folks will say “used it for xxxx and no problems. That’s EXACTLY like saying “smoked for 20 years and no health issues”. Can’t put it any simpler. The GM manual specifically calls for 10w30 and there are a lot of scientifically valid reasons. Go to shorter change intervals and accept shorter overall engine life and there are fewer reasons not to use 20w50.
Specifically, Valvoline has three grades of "Racing" oils, all with about 1200ppm of phosphorus in the form of ZDDP:
1) Valvoline Conventional Racing Oil has low detergent, and is NOT for street use. This is real racing oil.
2) Valvoline Synthetic Racing Oil also has insufficient detergents for street use. This too is real racing oil.
3) VR1 Racing oil is intended for street use and has adequate detergents. This is actually street oil with added ZDDP that cannot be legally added in oil and call it “street oil”-------it commands an extra price over “street oil” due to its “special name” and unique marketing strategy---------detergents compete with ZDDP and that’s why they are conspicuously absent from real racing oil
All three of the Valvoline "Racing" formulations at 1200ppm have adequate INITIAL ZDDP for high-performance applications. The valvoline VR-1 is an excellent oil for our cars IF you choose the CORRECT viscosity ie 10w30. But here is something to consider. A level of 1200ppm is proven adequate for high-performance flat-tappet engines, but due to depletion of the ZDDP molecule as it performs it's intended task, research shows that the concentration will drop as much as 25-40% within 1500 miles. This means that the ZDDP level will fall below safe levels at some point within the 3000 mile oil change interval. Extend the interval and the levels drop even further. They quickly reach levels below that of new SM oil in the .08 range.
Interesting enough a typical oil test will not show this depletion. Normal elemental analysis will show that the elements of zinc and phosphorous are still present but the multiple bonds that bind them into the ZDDP molecule are destroyed. Typical oil analysis is done using plasma coupled spectroscopy, but it merely shows the elements, not the molecules that they are part of. It is sort of like running a cow through a meat grinder. All the elements are still there. Everything that constituted a cow is on the plate but it’s not a cow anymore. Quantifying the actual oil ZDDP level requires advanced analysis techniques like FTIR. For more on this see this article:
Molecular Spectroscopy - A Precision Lubrication Tool? This kind of testing can cost hundreds of dollars per sample, and you will need to do multiple tests to show the initial value and trend. I know: I've spent thousands of dollars on this kind of testing.
So while VR-1 is a good product I feel an even better choice is a good grade of quality SM street oil bought at a discount. The savings will almost pay for the ZDDPlus. Add half a bottle of ZDDPlus to bring it up to the 1200 range. After 1500-2000 or so miles add the rest of the bottle to refresh the ZDDP levels and you are at peak protection for another couple thousand miles. If that seems like too much trouble you can add it all to begin with and start with ZDDP in the .18 range which is not going to hurt anything. This way you have a wide variety of oil to choose from at competitive market prices. You can’t do this with any available oil that I know of.
When the motor was torn down for the first time by Mike Doyle our mechanic at the time he couldn't believe it, he said the engine looked brand new with the usual cylinder wear. 
Oil was changes every 3,200mi. with a Fram filter.
