Mostly likely it has to do with the horribly shitty internal seals on the master and slave cylinders. That warning is probably the best acknowledgement we'll ever get from Nissan on the matter.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |