Which manual transmission should I use?

I drive an 04 Honda Accord 5 speed with 212,000 miles. What difference will it make if I use an oil other than Honda gear oil. Some people on various Honda forums recommend Amsoil or Synchromesh or others. I just replaced it yesterday with Pennzoil Synchromesh, but my mechanic expressed concern about this. What is your experience, and what do you recommend?

It shouldn't make any difference it is was the correct weight and type of oil recommended. (ex SVG, AGL, SVO, FGR, FGO) - it should be specified in the owners manual. Last time I changes a manual trans oil was in a 1982 Civic - it used 10w-30 I believe.

Yes