Scag Turf Tiger 61 deck with a 27 hp liquid cooled kawasaki engine with 1600 hrs is burning burning oil at a rate of about a half qt for every 8 hrs of operation. We do alot of large commercial properties and run these machines pretty hard. This one gets about 30 hrs runtime a week. I change the oil and filter every sunday and always use Penzoil SA 30. It spits black smoke when starting and when blades engage, but then exhaust runs clean. Dealership says run it till it blows and nothing can be done about it. Any suggestions for additives or oil that may increase the life of this engine? Thanks in advance.