in my '02 XJ8 5-speed when driving around town, max 45 MPH, is it better to put the gear selector in 4th to eliminate the auto trans from shifting in and out of 5th gear so much? I assume 5th gear is overdrive, is that right?

Doug

 

I would leave it in drive. TCM will select best gear for vehicle to be in.

 

and for best economy