As far as I can tell, both models use the same spark plugs, so why does the maintenance guide specifically call out the 821 needing to be changed twice as often (every 15k vs 30k)?
Most likely because the 821 was built first. I'd guess both motors are fine with a 30k change, but Ducati wasn't aware they could last that long in the testastretta 11° until they had extensive service records.
