Macbook Pro 15" burn DVD+R??

I am using Mac OS X 10.4, 2.16ghz intel core duo. I was wondering if there was any software that I could use to upgrade to allow me to burn DVD+R DL (8.5GB) disc. Or is it just not compatible with my laptop

I thought the MBP's SuperDrive (Even the Core Duo ones) could burn both + and - Formats, including RW's and Dual Layers.

That was my understanding when i purchased my MacBook Pro.

Check your system Profiler, I think some of the Superdrives can only do -R DL discs

Yeah I thought it would write DVD+R DL discs but cant get it to work either through toast or disk utility for some reason. Maybe it is not possible but my info about mac says:
MATSHITA DVD-R UJ-857:
Reads DVD: Yes
CD-Write: -R, -RW
DVD-Write: -R, -RW

so I assumed that I could write the dvds. Is there a difference between DVD+R DL and just normal DVD-R other than + are rewritable and maybe I can only use the - ones??

According to your system info, you can only write to (just like it says) DVD-R and DVD-RW. These are only 4.7GB discs.

You cannot burn DVD+R, DVD+RW, or anything DL (the 8.5GB discs).