I read a while back that these engines do best between 180 - 200 F but mine often gets to 210 - 215 F especially going up hills or when it is hot out. Sometimes it gets close to 220 F but not often. I don't tow anything, but it is a heavy step van. Should i start looking into ways to keep this cooler or are these temps normal? I use a 180 thermostat in summer and 195 in winter.
The thing that makes it complicated is that i rely on engine heat for my vegoil fuel system so i don't really want the engine to run much cooler, unless i could be damaging it.
thanks,
Paul

Sounds like you have a flow problem there somewhere. You should be running your 195 T-stat year round, not just in winter. Most any diesel will perform it's best around 195-200 degrees engine temp. 210 and up you need to keep an eye on it, and at 220 I would be backing out of it. Maybe a new water pump and a high flow t-stat with a better fan clutch would get your temps more consistent(key factor for longevity is consistency in temp, reduces metal fatigue).