break in oil really doesn't matter anymore, we get what comes from factory in new engines. going back the OP question, imho yes, 20 hrs on a new zero turn engine would warrant a change regardless even what the owners manual recommends. oil change intervals have been extended for enviro concerns, not the longevity of engines, etc in those manuals.... so make that 1st change now. & document for warranty.
yes to what has been suggested, use full syn engine oil,. & don't forget the initial hyd oil/filter change schedule, (go full syn for that as well) for engine oil, i use Rotella T6 on mowers & tractor. best regards
yes to what has been suggested, use full syn engine oil,. & don't forget the initial hyd oil/filter change schedule, (go full syn for that as well) for engine oil, i use Rotella T6 on mowers & tractor. best regards