if you want a high quality synthetic i recommend MTL-P from specialtyformulations.com. it is what i have in my xterra and i have MTL-R in my tacoma.
it is also 75w85 which is what nissan calls for. it is expensive but i believe it is worth it.shifting is smooth even in cold weather.amsoil also makes a manual transmission lube (MTG)that would also be an excellant choice.