Yes, I agree.
This is of course mostly for the lurkers out there...
Engine and Transmission are a bunch of metal parts - different metals - that fit together and - and a number of the parts either move or need to from an oil seal between them.
Things have to fit right.
Metals expand as temperature increases, shrink as temperature decreases.
Trouble is, different kinds of metal and metal alloys do this expansion and contraction at different rates.
http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
The engine will therefore be designed with a normal operating temperature.
A great example of operating temperature and metal expansion is the freaky case of the SR-71 and it’s fuel leakage on the ground until wings got up to temperature in flight.
The temperature of the engine is not the same all over; some parts are hottest, others less, still others are in a place where heat is dissipated quickly and they are relatively cool.
Car engines have bearings in them as well, which are precisely fitted and also have specified operating temperatures.
Operating the engine and transmission outside of their normal operating temperature ranges will cause excessive wear on parts that lubricating oil can not fully compensate for.
Also, as someone else noted, even at normal temperatures, operating a vehicle for extended periods near or beyond its normal operating limits or patterns (”beating” the car, etc.) will cause excessive wear.
I saw a guy drive his chevy impala (no slouch of a car back then) never use overdrive, but always use the top gear - a few years later his transmission needed to be rebuilt.
When two metal parts move against each other as they do in engines and transmissions, very small, tiny, pieces of metal are removed from one or the other or both parts. This is why the oild becomes darker in color; you’re seeing a cloud of minute metal shavings suspended in the oil. Of course, the oil between two moving parts will also contain the “shavings” - and make additional metal removal happen at an even faster rate than when the oil is brand new and clean. Viscosity breakdown is only part of the story of old oil; dirty oil may be the exact right viscosity specified, but will cause excessive wear.
Pressures between moving parts increase at different times and directions of movement in heavy throttle settings when under load. Thus, “pedal to the metal” causes excessive wear on engine and transmission parts, as does towing or carrying heavy loads.
I feel guilt. I have committed excessive wear on all my vehicles.