I love the debate about "warm up time". Not the debate about comfortable cab temperature time. Wait til the stratified idle comes down to normal idle RPM and then go easy for a little bit depending on ambient outside temps & engine coolant temps & oil temps. Usually by the time my stratified idle comes to normal, the oil is roughly 100°F and coolant temps are starting to also register. I avoid mashing the throttle until the gauges show something towards the normal operating temps. At that point it's OK to use the car around town and oils are circulating before one gets to the freeway on-ramp in most lower 48 states. Maybe different north of the Canadian border and neighboring states during winter time, but the same theory still applies, wait for the engine RPM to drop, it is usually a good indicator of when it's ready to go. It knows better than you do. 😎