I can warm up my truck by driving @ 55 mph in 5th gear at 2000 rpms, but it takes a long time to reach equilibrium coolant/oil temps .... I can warm up my truck by driving @ 55 mph in 4th gear @ 2500 rpms, in which case the oil/coolant will reach an equilibrium temp significantly faster. Engine wear is a function of "mean" piston speeds along with average rpms. However, conventional P/Zn/S, anti-wear additives typically don't become fully effective until bulk oil temps reach approx 140F/60C. Given this "Tradespace": 1) Which is the more effective strategy for minimizing engine/transmission wear during the warmup phase, and why? 2) Can the answer to #1 even be determined analytically, or strictly through a controlled experiment? 3) How dependent is the answer to #1 on the design and operating parameters of the engine & transmission? For example, pushrods vs DOHC, high rpm vs low rpm, gas vs diesel .... 4) Is the answer to # 1 completely independent of ambient temps during the warmup phase? Partial credit will be given, and all the heavy hitters get to play too ... Note: Automatic transmissions can easily be locked out of overdrive, so these questions have general applicability.