Humblecowboy

I reckon I will stay with the 190 as you guys suggest. I googled the Cummins T-stat and one link led me to a thread on Turbo diesel register and one of the guys stated that the 98.5 to 01.5 engines came with the 180. After that they went with the 190. Would running my CPL tell me the temp it was engineered for? Thing is, from what I'm finding on it, it has either been superseded or the replacement doesn't have the rubber gasket molded on it. Most of the links pointed so called Chinese made OEM's that I want nothing to do with. That's a way too expensive hunk of cast iron to trust to knock offs. I think I'll stick with the 190 and just get used to my gauge sitting higher than I've been used to for all these years. I would post the link to it but that might be a no no here so I'll stay away from that. There was one guy who posted some very good info on diesels and operating temps. He says they are best at the higher temps as y'all have told me. I promise I'll never cheat on DTR ever again.

KATOOM

The information some random members offer others is beside me.....

The 12 valve came with a 180*. There's been talk over that the first 24 valves in 1998.5 may have been equipped with a 180*, but if thats accurate then Dodge must have quickly realized the problem as all 24 valves thereafter came with the 190*. There are no upgrades non o-ring versions either as the design needs that o-ring in the thermostat housing in order to fit properly. Here's what it should look like. Replacement Parts (Engine Related) - Fourth Generation ('10 and Newer) - 190° THERMOSTAT KIT - GATES ('98.5-'09 and '13-'15, 6.7L - 5.9L) The Cummins OEM version can have a larger body.

And yes, diesels do need to run warm. People often mistake the operation of a diesel engine of that the same as a gasoline engine and think that you'd make more power with a 180* thermostat. Unfortunately thats not accurate, and especially on the 24 valve cylinder heads which flow too much air for the cooler 180* thermostat. As I pointed out earlier, a 200* thermostat will help increase fuel mileage but its too hot for towing and in hot climate areas.

Humblecowboy

That's exactly what the 190 is in my truck now except it's the Stant. Yeah, If I tried putting one in without that o-ring then I'd have a mess and need a long long water hose to keep it filled. LOL Y'allhave convinced me without a doubt to keep the 190. In all my years of mechanicing and cars I think the cooling system has always been my most important to make sure it's right. This truck is my first diesel and it still puzzles me at times. Thanks for the info, I've been through quite a learning process on that engine. I'm still wondering what I'm going to use that engine for after the chassis falls off around it.