4000 RPM is a bit high for "just driving around" ,unless you always drive like your ass is on fire
If your going for pure acceleration then yes ,5000 is a "decent" shift point.Your optimal performance shifting is going to be at a point where you have a good amount of torque in your gears.Our inline 6's aren't torque monsters and don't start pouring it on till the higher end.When I realy wanna get moving I try to nail my shifts around 5200 rpm.As for if that's "good for the car" ,it depends on the condition your car is currently in ,and you have to consider that fact that the harder you are on a car the shorter it's life is going to be.I suspect that my car had a bad crankshaft ,and after I beat the hell out of it in a parking lot I now have the engine in a million pieces in the garage.For shifting at the "optimal" range ,you first have to make sure your car is in sufficient shape ,and it's not something I would do often to a car I actualy relied on for transportation.The more relavent question is ,what condition is your motor in?