Synth Q's answered
Unlike most petroleum based lubricants, unless there is a HUGE difference in tempuratures ( HIGH compression or HUSE PSI), 520 or 5-30 makes little difference. Because of the closer tolerances, and better lubricants out there today, viscosity amkes little if any difference the higher you go. Personally, if we can run 0 weight oils in our turbines here in Hawaii, and I run 0-30 MOBIL1 in my newer cars, the lighter the oil, the better the power output on a well sealed engine, as less is lost in friction and more heat is picked up in a faster moving, lower gravity lubricant.
Please,all you physics and chemistry bubba's chime in here. But if a gas turbine can run at 1200 degrees C and 40k rpm on light oil, and my Mustang and Suburban can as well in the humid, salty hot climate of Hawaii, it'll run anywhere ('cept Maybe Yuma)!
My two cents
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