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you dont want a lower temp stat. in fact many people put 203* stats in to inprove engine performance:
WHY IS 203* BETTER THAN 195*?
Diesels run most efficiently at approximately 200*. A 195* thermostat will start to open at approximately 165*-170*. The Powerstroke has such an efficient cooling system, that this low flow when the thermostat is slightly open is normally enough to keep the engine cool. The downfall to this is that the engine -- when our trucks are not under load --never begins to reach its optimal operating temperature. Our 203* thermostat begins to open at 185*. This brings the operating temps up from about 170* to about 185*. This is closer to the operating temperature range that is preferable in our trucks for optimal efficiency.
When our trucks are under load and are producing higher combustion temperatures the 203* will allow the engine to run even closer to its optimal operating temperature. If the truck is under load and reaches the 203o setting, the thermostat is then fully open. This means you are at the maximum coolant temperature that the truck will reach. Your maximum temperatures are only a few degrees higher than in stock configuration, but these are degrees that you want for better performance. The best benefits come when the same truck is under a light load and would have a hard time reaching this optimal temperature. As stated above, you will never reach this optimum temperature with the stock 195* thermostat. The end result of installing the 203* thermostat should be slightly better fuel economy, less smoke, and maybe a few extra "ponies" to go along with it.
if you are having engine cooling problems than something is wrong
if you are looking for more power, once again a turbo diesel is not like a turbo gas engine
WLIHNTR.......where did that information come from? I am curious. I certainly do not doubt the info. Also, where would one procure said 203? We have a Ford Truck house here in Dallas that I use for parts.