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Discussion Starter #1
When I installed my Ram Air my fuel mileage jumped from 12 mpg to 14 mpg with my 454". At that time I was using a 195 degree thermostat. I tried using a 2400 cfm Derale electric fan but to make it work right I had to use a 180 degree thermostat. My fuel mileage immediately fell to 12 mpg and I couldn't understand why it dropped. After 6 months of use I abandoned the Derale but kept the 180 degree thermostat thinking it wouldn't hurt anything and it did provide ample heat from my heater. But a few days ago I installed another 195 degree thermostat and my fuel mileage went back to 14 mpg. I'm wondering if hotter engines DO provide better fuel mileage.


As an experiment I'm going to install a 205 degree thermostat and see if it increases my fuel mileage.
 

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Got MY 205 Degree Thermostat

My STANT 205 degree thermostat arrived this morning so I'll install it tomorrow morning just to see if it affects my fuel mileage. As it's pretty common for it to hit 205 degrees in the dead of summer I figure it won't hurt anything and it MAY increase my fuel mileage. I'll find out.
 

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Installed My New 205 Degree Thermostat

I installed my new 205 degree thermostat about two hours ago so now I'll see if my fuel mileage is affected. I'm hoping it'll increase to 75 mpg but 14 mpg would make me happy. I'm also hoping my horsepower will increase to 1000 or more but I won't hold my breath on that one.
 

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Does Hotter Engine Temperaures Equate To Better Fuel Mileage?

Since I installed my new 205 degree thermostat I have made two trips to the valley as well as picking up my mail several times. About 125 miles on 10 gallons of gas. For local trips 10 gallons usually gets me around 90 miles so there does seem to be an improvement. The acid test will be when I make the next Fresno trip running a constant 55 to 60 mph most of the time. I may end up very disappointed.
 

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Higher Engine Temperature

Since I installed the new 205 degree thermostat my '71 has seen a 21% increase in fuel mileage. I have made 4 round trips to the valley and back with each trip seeing around 20 stops (10 each way). I'll know more after I make a couple of Fresno trips which would involve 55 to 60 mph speeds and far fewer signals or stop signs. Hoping to get 14 mpg again.
 

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Higher Engine Temperatures Produce Better Fuel Mileage?

I just got back from Fresno and my trip meter is showing the usual 87 miles BUT I still have 1/4 tank left. In my 10 years of driving this thing it has NEVER gone this far on 3/4 tank of gas. And there was a LOT of traffic and road construction along the way so my average speed was around 45 to 50 mph. After running three tanks thru it it appears the hotter 205 degree thermostat IS producing much better fuel mileage.


I won't know for sure how much better it is until I make a longer trip at a steady 65 to 70 mph.
 

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Increased Fuel Mileage

I'm just finishing my 5th tank and still getting a 21% fuel mileage increase with the hotter 205 degree thermostat.
 

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Still Realizing A 21% Increase In Fuel Mileage

I just finished burning up my 6th tank of gas and I'm still getting a 21% increase in my fuel mileage after installing the hotter 205 degree thermostat. The higher engine temperature has increased the thermal efficiency of my engine. I had been running a 180 degree thermostat because I had used it when I was experimenting with a Derale electric fan several years ago. When that thermostat stuck open recently I installed a 195 degree thermostat and my fuel mileage instantly increased by about 15%. So I decided to try a 205 degree thermostat and it increased by another 6%. Proof of better thermal efficiency and better fuel mileage.
 
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