The motors were designed to be most efficient at 195. However SC'* build lots of heat and once you pulley...it'* a smoking motor. To keep it reasonable the 180 is necessary.

Most NA'* that do the 180 is in an attempt to keep the motor cooler and prolong the upper intake from getting brittle from heat and cracking.

This may not relate since the cooling systems are somewhat different, but I didn't notice any significant impact to the cabin heater when I went from a 195 to a 180 t-stat in my Regal. Gas mileage lost a little, but the heater still blows plenty hot and it still heats up just as fast, it just stops at a lower temp. Air being exchanged across 180 degrees versus across 195 is not that much different, and both are damn hot.

OK, but understand that when it comes to heat exchange and the heating/cooling cycles in your vehicle, here are some factors to consider:

- It'* only 15* difference, BUT that 15* becomes MUCH more important when you consider that the heating/cooling difference is additive. The heater blower is re-circulating the cabin air (unless you have it set for outside air - unusual). That means that for every heating cycle, you are taking that cabin air (15* warmer than w/ the 180* 'stat) and heating it up again. Thereby raising the temp. another 15* above where it would be w/ the 180* 'stat. See how quickly this adds up to a much warmer cabin temp in a quicker time period?

The above example is just for illustration, as the 15* 'stat difference doesn't really translate into a full 15* difference in cabin temp. per cycle, but you see my point?

Lash...doesn't the system default to outside air? And you must choose recirc.

I agree that it will make a difference, but I'm just saying that in my experience, the difference isn't that much, unless the heat exchanger in the Regal is more efficient than that in the Bonneville. I also very seldom run in Recirculate mode in either my Regal or my Bonneville (I do when the AC is on or if there is an unpleasant odor outside), so that additive factor that you describe doesn't apply. In short, you will get hotter air from the 195 t-stat, but unless it is brutally cold outside, a person would have a hard time feeling the difference. It certainly shouldn't feel flat out cold unless the t-stat is opening much earlier than it should.

You know, you might have me there. I didn't consider that since my SE is a very base model and has manual controls. Therefore I mostly choose recirc, as that is the most efficient at heating or cooling. That is, unless your outside ambient air temp happens to be closer to your desired result than the cabin temp - like when it'* been parked outside in the sun and it'* 2000* degrees inside and ONLY 98* outside.

Anyway, for all those that didn't know already, recirc is your friend, for the reason posted above.

Well I tried that and It was pretty clean.

I have to admit that the car does warm up as everyone said it would, it seems that since the stat change the ECC temp setting needs to be about 6 or 7 degrees higher than what it was, I can live with that.....
thanks to all that replied......