I rebuilt the motor in my 95 model ram after 192,000 miles. Both heads were cracked. Found another set, again both cracked. Found a 3rd set off of a totaled truck with only 26,000 miles on it.......both cracked. Finally bought some reman heads and put a 180 degree in it. Not only will it reduced the chance of the heads cracking again, but no more annoying spark knock! gas mileage suffering was minimal. still hitting 14.5-15.0 mpg. If anybody is gonna whine over loss of performance in changing a thermostat, then chances are they never had enough power in the first place.