Do i need gutmann?

I sold a hard drive on ebay bundled with a computer. I had some private stuff on the drive so i decided i should wipe it clean. Right now its running the Gutmann erasure method. I have 4 of 35 passes. Think this is good enough? Should i wait for it to completely finish? For all i know this guy isnt going to try recovery AT ALL.

Unless you're doing al-qaeda stuffs in there, even single pass should be enough !