Mike - I'm surprised the viscosity for this oil took such a hit since 300V is such a robust oil. Is this before you added the oil cooler? TBN was high so the oil had plenty of life left in it.

It should be the newest formulation as that came out at the end of 2012 (Ester Core).

-Dennis

No oil cooler yet. We wanted to baseline everything before making those changes.

We will report back after the next oil change which will have 70/30 split using no cooler and the 2015 DIT cooler.

Mike

Really depends on how often you want to overhaul... assuming ethter / pao or paraffin oils with right additives (my understanding is that it really is the additives if you have constant operating environment)...;
1) 0W-16 if you can overhaul anytime
2) 40 grade, if you intend to run for couple of years, maybe like 10,000km/year, with intervals (i.e. HPDE or multiple race weekends / tests)
3) 60 grade, if you are doing 24hr endurance

I've used 0W-40 Mobil1, run 95℃ - 105℃, changed every weekend of racing / tests, and run 12,000km this year on track. I expect to overhaul next year, based on how other cars failed with similar use profile. Expensive hobby indeed.