How much free memory is needed?

I don't know, is the unit functioning properly? If it works okay then you're alright. You might consider more memory before the next map update though.

"If it ain't broke don't fix it"

ummmm.. depends on how much your looking to load

probably, but you have little leeway left for new POI files

I assume you have cleared out the files that you do not need.

Let me illustrate with my 765T

(note all numbers are expressed in MB and I have not deleted any files to gain space)

Garmin Nuvi size=2976 (free = 704)

Garmin Root (18 files) size = 1970 (includes all maps plus files like current.m3u8 (my playlist of audio files), GarminDevice.xml, locales.xml (gives data such as decimal separator and date format for various countries), prodkey.bin, and all maps files (with gmapprom.img being the largest at size = 1528)

Garmin\JVC size = 757

Garmin\Voice size = 372

Audible (26 files) size = 62 (mp3 files that I listen to while driving)

Garmin\POI size = 17

Garmin\ExtData size = 14

Garmin\Vehicle size = 12

Garmin\Help size = 12

Garmin\Text size = 11

Garmin\GPX size = 4

plus other files/folders whose size is less than the 3 MB you have left.

Where might I gain space?

Garmin\Voice has 124 files, but all I use is "Jill". The voice files are in sets - a .sum file and a .vpm file. If I decided to keep all of the "English" voices I could remove 276 MB. If I also got rid of "Australian" and "British", I could save 65 MB more.

I don't really need my audio files.

If I got rid of all vehicles except car-blue.srf, I could save 11 MB.

If I got rid of all Help files except American English, I could save over 11 MB.

If I got rid of all Text files except British_English.gtt, British_English_Prx.gtt, and British_English_Trf.gtt, I could save 10 MB.

So, it looks like I could gain about 373 MB (not counting my audio files).

In a pinch, one might be able to get a JVC file that is smaller (less detail, etc). If someone knows whether or not Nuvis will operate without a JVC file at all, please chime in.

AS ALWAYS - do not make any changes to your GPS (with the exception of loading POIs) without doing a full backup.

I would be concerned with only 3 MB of free space because of the trip log recording in current.gpx. Note that the trip log continues to record points (up to 10000 points) even if your have the trip log display turned off. It then copies these points into current.gpx. I am not sure what will happen if your nuvi runs out of memory and can't expand current.gpx to hold all of the trip log when it boots up. I suspect it may lock up.

should be okay.