[ECONORAM]

I realize this thread has been dormant a while, but it touches a few things I have been stewing over.

Originally Posted by BIG DAVE

I use a 203 degree thermostat, and Evans propylene/ethylene glycol coolant.

I gained 0.5 MPG by doing this. One of the few engine mods I've seen work.

Originally Posted by diesel_john

I run pure Seirra antifreeze in a cast iron block with aluminum heads. i did it to help prevent detonation. I boiled the water out of the mixture by turning off the fans and taking off the rad cap and letting ti idle until it got to 250 f and there were no more bubbles coming out. It doesn't even boil at 250 now with the cap off. no steam separation in the heads equals a better resistant to detontion. the solution is a little bit more viscous than 50/50 make sure you have a good enough water pump on cold starts to circulate in the block and the stock thermostat will run hotter because of this. i always take out the thermostat and drill a 1/16th hole thur it if its doesn't have a little air bypass check valve built in.

I realize both of your vehicles are diesels. I was also thinking of switching to Evans Engineering coolant, but I think my truck would require a custom tune to take advantage of the added temperature range. (OEM T-stat is 193.) I thought it might also give an mpg boost, since it'd be retaining more of the combustion energy...instead of wasting it by cooling.
Never thought of drilling a pilot hole in the T-stat. Did you do that even before the coolant swap? I did think about redesigning a T-stat, so it was a butterfly valve that pivoted like a throttle plate, instead of that blob in the pipe...but that would take some work.

Originally Posted by MetroMPG

I can't answer the thermal stress question, but do have another one: will your engine let you run at higher temps? What's your electric fan's trigger temp?

Temp is a tricky issue because another effect of more heat is less timing advance (engine may be more likely to ping the hotter it gets).

I'd like to raise my truck's running temps to pursue better mpg, but my truck's PCM will pull timing if the water temp is too high. I have installed a warm air intake and an under drive crank pulley. The Taurus e-fan keeps temps in check, but the WAI makes the tranny downshift out of 5th lock sooner (grrrr).

Evans advises everyone using it to run a non-pressure coolant cap, or the fluid will never boil...which would make it less effective. I don't think gaskets would be a problem with Evans coolant (boils at 375* at 0 psi), but the timing loss in my truck would make it a dismal mod, I think. And...just because the coolant is hotter doesn't mean combustion is any hotter, does it? Hmmm, might even be able to delete the radiator fan...would definitely need a digital temp gauge.