Well....This could raise more ire than the previous paint scheme debate, but here goes. I operate a R-3350, a wright 975-E3 and an M14P, all on Phillips 25w60. I also have tremendous respect for John Lane's opinion, but I have done a lot of research on this issue and I kind of come at this from a different angle. I think the 25w60 handles heat very well and doesn't suffer viscosity degradation as readily.
First, I firmly believe that all major brands of oil sold today are far superior to any of their original (old) counterparts. I have a North American Yale (Wright 975-e3) and it, as with all Yales, tends to run with a very high oil temp normally. Rebuilt the oil cooler, rebuilt all baffling and still had high temps. I was running Aeroshell 120 and had several conversations with Shell and one of the
Shell factory experts actually reccomended that I try a multi viscosity oil. Phillips 25w60 runs almost 10 degrees cooler in my particular application.
By far the most important consideration is operating at proper temperatues, correct capacities and regular and timely oil changes.
In many ways I think this is a "ford" or "chevy" sort of debate.
I am a very strong believer in the need for aftermarket filteration. I use the Aviation Development Corporation filters on my engines (
www.aviationdevelopment.com). I particularly like the fact that they don't have any signifigant addditional capacity and they give a bypass indication very quickly when the micro screen is contaminated with anything. The heat sink design also provides some additional heat dissipation.