Let me try again. I don't know where the 2500 number came from either, I always "hear" 3000. As far as "scientific evidence", you won't find ONE definitive answer. There is no one magic number, it varies for may reasons, and no obvious harm will be done within a wide range of operation.
I also agree that Manufacuter's recommendations are driven by many factors other than our best interest.
That Hot Rod article has nothing to do with engine warmup, the are referring to continuous low operating temperatures.
What racing teams do has no relation to street driving. Racers want everything at full operating temperature before going on track because "putting" around is hazardous, a waste of track time, and they want maximum H.P. right away.
IMO it works out like this: 2000 is about the lowest operating RPM where the engine pulls well without lugging, which is also hard on the engine (bearings). Staying above this RPM when upshifting, with an average RPM drop of 1000, puts you at around 3000. I agree that the object is to put minimal load on the engine during warmup, so I only use 1/4 throttle.
During cold winter days I will Idle longer than my normal 60 Seconds.
Just my ¢
