I just bought a Toro Z597 as some of you know. Its the 27hp diehatsu (sp?) diesel. Its got the biggest hydro pumps out of all the toros and is very well built. What do people get out of their diesel ZTR's 4000 hrs? 5000 hrs? 6000hrs ? Also, what do people run their gas mowers (25+hp / Liquid cooled) too? I can see running a HIGH HR mower as a backup or to speed up production but as far as your primary steak & potatoes? This mower cuts 90% of my municiple contracts im trying to figure out at what point i would replace it and move it down the line to "backup" status. It will get 1100hrs/yr and i have a 3 yr contract. Do i replace it if i sign again in 3 years or do i run it to 6600 hours and hope for no break downs? (an extra 15g in pocket or 5g a year) Looking for opinions, facts, or experiences with ZTR's gas or diesel.