DM2 and DM3 maintenance.
DM2 and DM3 engines are similar.
change engine oil every 100 hours or so, suggest oil filter at the same time.
Check oil levels daily before departure that level is in range
Fuel filter - again once a year, more if you do longer trips.
Check tappets several times a year.
Air filter - clean and check the gauze,
Walter / antifreeze - check level daily, change annually
Water pump - depending on type = grease all bits daily before setting off is the best advise..