My RX300 was preowned by someone who lived downtown in a large city. I live in the suburbs of a smaller city. Does this ECU 'learn?' Should I reset it? What benefits, if any, should I see? There seems to be nothing wrong with the car now...and I don't want to break anything.

 

Don't worry, you won't break anything

What I would suggest is the following (in more extensive format):

With the key out of the ignition and the vehicle off do the following:

1. Open hood and remove the EFI Fuse (see photo below) that is located in the fusebox near your airbox.

2. Keep the fuse out and then pull both the negative and positive battery cables off. Wait at least 30 minutes (oh I have heard about doing this overnight, but can't figure out why) and then put the fuse back in and reconnect the cables.

3. Initially, whe you turn on you RX, it may sound like its choking for air...wait a few seconds and eventuall the RPMS will kick up high 1,000+ RPM and then should after a short bit in Drive, it should get back to around 750 RPM.

4. The total amount of time it needs to learn can vary. At the track, it takes at a minimum 2 1/4 mile runs to get set, but sometimes I need 4 in the hotter months. I remember people used to think 100 to 200 miles. That may be the case more so with MPG, but for readiness monitors (such as used in an OBDII emissions test), about an hour of driving (50% highway, 50% city) should see everything about the way its going to feel until you do this procedure the next time.