30w was the oil used for lubricated torque in the studies I've found. Also it's the only way to get repeatable clamping values: dry torque will take about 10% more torque each time to achieve the same clamp force. It's surely why TTY is used whenever a tight tolerance is needed for clamp force.

I know ARP requires the use of their propriety lube for proper torque values with their engine fastener kits.


2002 X5 3.0 383,600 miles
2014 428i 71,700 miles


2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles


1970 Firebird under restoration - engine rebuilt with ARP bolts & studs