Temperature / thermostat and fuel economy

[curmudge1]

In an earlier discussion, someone suggested that, for those who don't tow (commuters), the stock 195degF thermostat would likely produce better mileage than a 185degF T-stat. So, my temps are registering about 185 since a new stock T-stat last winter, and I used to always register 195degF before that. So, I'm thinking about replacing the thermostat for better fuel economy, looking to return to the 195degF temps.

Anyone care to contribute any thoughts on the subject? TIA.

[damork]

I'm running twin 180's after the timing gear/'97 water pump upgrade. Mileage seemed to drop slightly after the upgrade, but I blame it more on the timing done rather than the thermostat as I was running a 180 before and gauge temp has not changed. I need to find somewhere that will time it and let me know for sure I have -1.94 offset. The dealers don't cooperate in all cases when looking under the hood, which was my case.

The single Robertshaw 180F thermostat last year got the highest mileage I've ever pulled with the truck then - 20.5 mpg. This was on a hot day (100F) driving 60-65 in rolling hill country - no load behind.

[moondoggie]

Good Day!

I think in theory the hotter you can SAFELY run, the better the mpg, but it depends on way more factors than I can collate. I think John Kennedy feels this way too.

Blessings!

Brian Johnson, #5044

[charliepeterson]

195* is the optimum temperature for performance and mileage. Depending on how you run dictates how you cheat to get there.

[richard7]

The engine efficiency is increased with a higher operating temperature, because less energy is lost through the heads and cylinder walls. More pressure (and energy) is avalaible to push the pistons.

Remember that pressure and temperature are linked together. When you compress air, it will heat :D , but when the air expands, like when the piston goes down on the power stroke, the temperature of the gases is dropping accordingly. More heat transfer to the engine walls will reduce the pressure further. A higher engine temp. reduce that heat transfer, leaving more pressure to pushhhhh.

[LanduytG]

I have been running 205* stats and will never go back. I tow with them as well and the they pulls hard. Last summer on a trip pulling about 7k I got my highest milage ever (14.2) before I would always average about 12.5. My dad a diesel mechanic all his life always said the hot you can run a diesel the better.

Greg

[kowsoc]

Greg, do you have a make and part # for the 205's. I had run them before in some gas powered vehicles I owned and they helped mileage. I have been happy with 195's in my 6.5....doesn't affect cooling at all because a thermostat opens wide open when cooling is needed. They are also good in cold weather for extra cab heat. The 195's definitely helped my fuel economy somewhat.

[heavydutydieselman3]

Originally posted by kowsoc:
Greg, do you have a make and part # for the 205's. I had run them before in some gas powered vehicles I owned and they helped mileage. I have been happy with 195's in my 6.5....doesn't affect cooling at all because a thermostat opens wide open when cooling is needed. They are also good in cold weather for extra cab heat. The 195's definitely helped my fuel economy somewhat. very interesting. love to hear some more on this subject. just goes to show ya you learn something new everyday. thanks guys. hddm3 :D

[LanduytG]

I sell Evan's Coolant so i got them from Evan's. Bit they are Robert Shaw stats so they should be easy to get. If not let me know and can get them.

Greg

[turbovair]

A diesel engine is a "heat" engine. The hotter it runs, the more power and efficiency it produces. However, you run up against some limitations such as metalurgy and lubrication which limit its max survivable operating temperature.Run the highest stats you can.I run a pair of 195's here in Phoenix.The difference between a 195 and a 180 stat in the event of overheating equals only a few additional seconds to the operator.If you run 180's and still push the temp limits, something is wrong with either the cooling system or the engine itself.

[billg]

I would like to try the 205s, but it seems that my truck doesn

[heavydutydieselman3]

Originally posted by turbovair:
A diesel engine is a "heat" engine. The hotter it runs, the more power and efficiency it produces. However, you run up against some limitations such as metalurgy and lubrication which limit its max survivable operating temperature.Run the highest stats you can.I run a pair of 195's here in Phoenix.The difference between a 195 and a 180 stat in the event of overheating equals only a few additional seconds to the operator.If you run 180's and still push the temp limits, something is wrong with either the cooling system or the engine itself. thanks turbo. sounds like you know what your talking about. i'll try the 195's or 205's. thanks again guy's. hddm3